Electrical contacts on a medical device patch

ABSTRACT

A device for conveying power from a location external to a subject to a location within the subject may include a flexible carrier and an adhesive on a first side of the carrier. A coil of electrically conductive material may be associated with the flexible carrier. A mechanical connector may be associated with the carrier opposite the adhesive, wherein the mechanical connector is configured to retain a housing and permit the housing to rotate relative to the flexible carrier. At least one electrical portion may be associated with the carrier in a manner permitting electrical connection to be maintained between the flexible carrier and the housing as the housing is rotated.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/355,981, filed Nov. 18, 2016, now U.S. Pat. No. 9,993,652, which is acontinuation of U.S. patent application Ser. No. 14/059,651, filed Oct.22, 2013, now U.S. Pat. No. 9,504,828, issued Nov. 29, 2016, which is acontinuation of U.S. patent application Ser. No. 13/952,027, filed Jul.26, 2013, now U.S. Pat. No. 8,948,871, issued Feb. 3, 2015, which claimsthe benefit of priority under 35 U.S.C. § 119(e) to U.S. ProvisionalApplication No. 61/676,327, filed Jul. 26, 2012, the entire contents ofall of which are incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the resent disclosure generally relate to devices andmethods for modulating a nerve. More particularity, embodiments of thepresent disclosure relate to devices and methods for modulating a nervethrough the delivery of energy via an implantable electrical modulator.

BACKGROUND

Neural modulation presents the opportunity to treat many physiologicalconditions and disorders by interacting with the body's own naturalneural processes. Neural modulation includes inhibition (e.g. blockage),stimulation, modification, regulation, or therapeutic, alteration ofactivity, electrical or chemical, in the central, peripheral, orautonomic nervous system. By modulating the activity of the nervoussystem, for example through the stimulation of nerves or the blockage ofnerve signals, several different goals may be achieved. Motor neuronsmay be stimulated at appropriate times to cause muscle contractions.Sensory neurons may be blocked, for instance to relieve pain, orstimulated, for instance to provide a signal to a subject. In otherexamples, modulation of the autonomic nervous system may be used toadjust various involuntary physiological parameters, such as heart rateand blood pressure. Neural modulation may provide the opportunity totreat several diseases or physiological conditions, a few examples ofwhich are described in detail below.

Among the conditions to which neural modulation may be applied isobstructive sleep apnea (OSA). OSA is a respiratory disordercharacterized by recurrent episodes of partial or complete obstructionof the upper airway during sleep. During the sleep of a person withoutOSA, the pharyngeal muscles relax during sleep and gradually collapse,narrowing the airway. The airway narrowing limits the effectiveness ofthe sleeper's breathing, causing a rise in CO₂ levels in the blood. Theincrease in CO₂ results in the pharyngeal muscles contracting to openthe airway to restore proper breathing. The largest of the pharyngealmuscles responsible for upper airway dilation is the genioglossusmuscle, which is one of several different muscles in the tongue. Thegenioglossus muscle is responsible for forward tongue movement and thestiffening of the anterior pharyngeal wall. In patients with OSA, theneuromuscular activity of the genioglossus muscle is decreased comparedto normal individuals, accounting for insufficient response andcontraction to open the airway as compared to a normal individual. Thislack of response contributes to a partial or total airway obstruction,which significantly limits the effectiveness of the sleeper's breathing.In OSA patients, there are often several airway obstruction eventsduring the night. Because of the obstruction, there is a gradualdecrease of oxygen levels in the blood (hypoxemia). Hypoxemia leads tonight time arousals, which may be registered by EEG, showing that thebrain awakes from any stage of sleep to a short arousal. During thearousal, there is a conscious breath or gasp, which resolves the airwayobstruction. An increase in sympathetic tone activity rate through therelease of hormones such as epinephrine and noradrenaline also oftenoccurs as a response to hypoxemia. As a result of the increase insympathetic tone, the heart enlarges in an attempt to pump more bloodand increase the blood pressure and heart rate, further arousing thepatient, After the resolution of the apnea event, as the patient returnsto sleep, the airway collapses again, leading to further arousals.

These repeated arousals, combined with repeated hypoxemia, leaves thepatient sleep deprived, which leads to daytime somnolence and worsenscognitive function. This cycle can repeat itself up to hundreds of timesper night in severe patients. Thus, the repeated fluctuations in andsympathetic tone and episodes of elevated blood pressure during thenight evolve to high blood pressure through the entire day.Subsequently, high blood pressure and increased heart rate may causeother diseases.

Efforts for treating OSA include Continuous Positive Airway Pressure(CPAP) treatment, which requires the patient to wear a mask throughwhich air is blown into the nostrils to keep the airway open. Othertreatment options include the implantation of rigid inserts in the softpalate to provide structural support, tracheotomies, or tissue ablation.

Another condition to which neural modulation may be applied is theoccurrence of migraine headaches. Pain sensation in the head istransmitted to the brain via the occipital nerve, specifically thegreater occipital nerve, and the trigeminal nerve. When a subjectexperiences head pain, such as during a migraine headache, theinhibition of these nerves may serve to decrease or eliminate thesensation of pain.

Neural modulation may also be applied to hypertension. Blood pressure inthe body is controlled via multiple feedback mechanisms. For example,baroreceptors in the carotid body in the carotid artery are sensitive toblood pressure changes within the carotid artery. The baroreceptorsgenerate signals that are conducted to the brain via theglossopharyngeal nerve when blood pressure rises, signaling the brain toactivate the body's regulation system to lower blood pressure, e.g.through changes to heart rate, and vasodilation/vasoconstriction.Conversely, parasympathetic nerve fibers on and around the renalarteries generate signals that are carried to the kidneys to initiateactions, such as salt retention and the release of angiotensin, whichraise blood pressure. Modulating these nerves may provide the ability toexert some external control over blood pressure.

The foregoing are just a few examples of conditions to whichneuromodulation may be of benefit, however embodiments of the inventiondescribed hereafter are not necessarily limited to treating only theabove-described conditions.

SUMMARY

A device for conveying power from a location external to a subject to alocation within the subject may include a flexible carder. An adhesivemay be on a first side of the carrier, and a coil of electricallyconductive material may be associated with the flexible carrier. Amechanical connector may be associated with the carrier, opposite theadhesive, wherein the mechanical connector is configured to retain ahousing and permit the housing to rotate relative to the flexiblecarrier. Additionally, at least one electrical portion may be associatedwith the carrier in a manner permitting electrical connection to bemaintained between the flexible carrier and the housing as the housingis rotated.

In some embodiments, a device for conveying power from a locationexternal to a subject to a location within the subject may include ahousing. An electronics portion may be disposed within the housing. Amechanical connector may be associated with the housing, and may beconfigured to retain a flexible carrier and to permit the housing torotate relative to the flexible carrier. Additionally, at least oneelectrical connector may be associated with the housing in a mannerpermitting electrical connection to be maintained between the housingand the flexible carrier as the housing is rotated.

In some embodiments, a device for conveying power from a locationexternal to a subject to a location within the subject may include aflexible carrier having a receiver. A coil of electrically conductivematerial may be associated with the flexible carrier. A housing,including a mechanical connector, may be configured to mate with thereceiver and permit the housing to rotate relative to the flexiblecarrier. At least one electrical connector may be associated with thehousing in a manner permitting electrical connection to be maintainedbetween the housing and the flexible carrier as the housing is rotated.

Additional features of the disclosure will be set forth in part in thedescription that follows, and in part will be obvious from thedescription, or may be learned by practice of the disclosed embodiments.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thedisclosure and, together with the description, serve to explain theprinciples of the embodiments disclosed herein.

FIG. 1 schematically illustrates an implant unit and external unit,according to an exemplary embodiment of the present disclosure.

FIG. 2 is a partially cross-sectioned side view of a subject with animplant unit and external unit, according to an exemplary embodiment ofthe present disclosure,

FIG. 3 schematically illustrates a system including an implant unit andan external unit, according to an exemplary embodiment of the presentdisclosure.

FIG. 4 is a top view of an implant unit, according to an exemplaryembodiment of the present disclosure.

FIG. 5 is a top view of an alternate embodiment of an implant unit,according to an exemplary embodiment of the present disclosure.

FIG. 6 illustrates circuitry of an implant unit and an external unit,according to an exemplary embodiment of the present disclosure.

FIG. 7 illustrates a graph of quantities that may be used in determiningenergy delivery as a function coupling, according to an exemplarydisclosed embodiment.

FIG. 8 depicts a graph illustrating non-linear harmonics.

FIG. 9 depicts a graph of quantities that may be used in determiningenergy delivery as a function coupling, according to an exemplarydisclosed embodiment.

FIG. 10 illustrates additional features of one embodiment of implantunit 110.

FIGS. 11a, 11b, and 11c illustrate a double-layer crossover antenna.

FIGS. 12a and 12b illustrate an exemplary embodiment of an externalunit.

FIG. 13 depicts a self-resonant transmitter employing a modified class Damplifier.

FIG. 14 depicts a pulsed mode self-resonant transmitter.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings, Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Embodiments of the present disclosure relate generally to a device formodulating a nerve through the delivery of energy. Nerve modulation, orneural modulation, includes inhibition (e.g. blockage), stimulation,modification, regulation, or therapeutic alteration of activity,electrical or chemical, in the central, peripheral, or autonomic nervoussystem. Nerve modulation may take the form of nerve stimulation, whichmay include providing energy to the nerve to create a voltage changesufficient for the nerve to activate, or propagate an electrical signalof its own. Nerve modulation may also take the form of nerve inhibition,which may including providing energy to the nerve sufficient to preventthe nerve from propagating electrical signals. Nerve inhibition may beperformed through the constant application of energy, and may also beperformed through the application of enough energy to inhibit thefunction of the nerve for some time after the application. Other formsof neural modulation may modify the function of a nerve, causing aheightened or lessened degree of sensitivity. As referred to herein,modulation of a nerve may include modulation of an entire nerve and/ormodulation of a portion of a nerve. For example, modulation of a motorneuron may be performed to affect only those portions of the neuron thatare distal of the location to which energy is applied.

In patients with OSA, for example, a primary target response of nervestimulation may include contraction of a tongue muscle (e.g., themuscle) in order to move the tongue to a position that does not blockthe patient's airway. In the treatment of migraine headaches, nerveinhibition may be used to reduce or eliminate the sensation of pain. Inthe treatment of hypertension, neural modulation may be used toincrease, decrease, eliminate or otherwise modify nerve signalsgenerated by the body to regulate blood pressure.

While embodiments of the present disclosure may be disclosed for use inpatients with specific conditions, the embodiments may be used inconjunction with any patient/portion of a body where nerve modulationmay be desired. That is, in addition to use in patients with OSA,migraine headaches, or hypertension, embodiments of the presentdisclosure may be use in many other areas, including, but not limitedto: deep brain stimulation (e.g., treatment of epilepsy, Parkinson's,and depression); cardiac pace-making, stomach muscle stimulation (e.g.,treatment of obesity), back pain, incontinence, menstrual pain, and/orany other condition that may be affected by neural modulation,

FIG. 1 illustrates an implant unit and external unit, according to anexemplary embodiment of the present disclosure. An implant unit 110, maybe configured for implantation in a subject, in a location that permitsit to modulate a nerve 115. The implant unit 110 may be located in asubject such that intervening tissue 111 exists between the implant unit110 and the nerve 115. Intervening tissue may include muscle tissue,connective tissue, organ tissue, or any other type of biological tissue.Thus, location of implant unit 110 does not require contact with nerve115 for effective neuromodulation. The implant unit 110 may also belocated directly adjacent to nerve 115, such that no intervening tissue111 exists.

In treating OSA, implant unit 110 may be located on a genioglossusmuscle of a patient. Such a location is suitable for modulation of thehypoglossal nerve, branches of which run inside the genioglossus muscle.Implant unit 110 may also be configured for placement in otherlocations. For example, migraine treatment may require subcutaneousimplantation in the back of the neck, near the hairline of a subject, orbehind the ear of a subject, to modulate the greater occipital nerveand/or the trigeminal nerve. Treating hypertension may require theimplantation of a neuromodulation implant intravascularly inside therenal artery or renal vein (to modulate the parasympathetic renalnerves), either unilaterally or bilaterally, inside the carotid arteryor jugular vein (to modulate the glossopharyngeal nerve through thecarotid baroreceptors). Alternatively or additionally, treatinghypertension may require the implantation of a neuromodulation implantsubcutaneously, behind the ear or in the neck, for example, to directlymodulate the glossopharyngeal nerve.

External unit 120 may be configured for location external to a patient,either directly contacting, or close to the skin 112 of the patient.External unit 120 may be configured to be affixed to the patient, forexample, by adhering to the skin 112 of the patient, or through a bandor other device configured to hold external unit 120 in place. Adherenceto the skin of external unit 120 may occur such that it is in thevicinity of the location of implant unit 110,

FIG. 2 illustrates an exemplary embodiment of a neuromodulation systemfor delivering energy in a patient 100 with OSA. The system may includean external unit 120 that may be configured for location external to thepatient. As illustrated in FIG. 2, external unit 120 may be configuredto be affixed to the patient 100. FIG. 2 illustrates that in a patient100 with OSA, the external unit 120 may be configured for placementunderneath the patient's chin and/or on the front of patient's neck. Thesuitability of placement locations may be determined by communicationbetween external unit 120 and implant unit 110, discussed in greaterdetail below. In alternate embodiments, for the treatment of conditionsother than OSA, the external unit may be configured to be affixedanywhere suitable on a patient, such as the back of a patient's neck,i.e. for communication with a migraine treatment implant unit, on theouter portion of a patient's abdomen, i.e. for communication with astomach modulating implant unit, on a patient's back, i.e. forcommunication with a renal artery modulating implant unit, and/or on anyother suitable external location on a patient's skin, depending on therequirements of a particular application.

External unit 120 may further be configured to be affixed to analternative location proximate to the patient. For example, in oneembodiment, the external unit may be configured to fixedly or removablyadhere to a strap or a band that may be configured to wrap around a partof a patient's body. Alternatively, or in addition, the external unitmay be configured to remain in a desired location external to thepatient's body without adhering to that location.

The external unit 120 may include a housing. The housing may include anysuitable container configured for retaining components. In addition,while the external unit is illustrated schematically in FIG. 2, thehousing may be any suitable size and/or shape and may be rigid orflexible. Non-limiting examples of housings for the external unit 100include one or more of patches, buttons, or other receptacles havingvarying shapes and dimensions and constructed of any suitable material.In one embodiment, for example, the housing may include a flexiblematerial such that the external unit may be configured to conform to adesired location. For example, as illustrated in FIG. 2, the externalunit may include a skin patch, which, in turn, may include a flexiblesubstrate. The material of the flexible substrate may include, but isnot limited to, plastic, silicone, woven natural fibers, and othersuitable polymers, copolymers, and combinations thereof. Any portion ofexternal unit 120 may be flexible or rigid, depending on therequirements of a particular application.

As previously discussed, in some embodiments external unit 120 may beconfigured to adhere to a desired location. Accordingly, in someembodiments, at least one side of the housing may include an adhesivematerial. The adhesive material may include a biocompatible material andmay allow for a patient to adhere the external unit to the desiredlocation and remove the external unit upon completion of use. Theadhesive may be configured for single or multiple uses of the externalunit. Suitable adhesive materials may include, but are not limited tobiocompatible glues, starches, elastomers, thermoplastics, andemulsions.

FIG. 3 schematically illustrates a system including external unit 120and an implant unit 110. In some embodiments, internal unit 110 may beconfigured as a unit to be implanted into the body of a patient, andexternal unit 120 may be configured to send signals to and/or receivesignals from implant unit 110.

As shown in FIG. 3, various components may be included within a housingof external unit 120 or otherwise associated with external unit 120. Asillustrated in FIG. 3, at least one processor 144 may be associated withexternal unit 120. For example, the at least one processor 144 may belocated within the housing of external unit 120. In alternativeembodiments, the at least one processor may be configured for wired orwireless communication with the external unit from a location externalto the housing.

The at least one processor may include any electric circuit that may beconfigured to perform a logic operation on at least one input variable.The at least one processor may therefore include one or more integratedcircuits, microchips, microcontrollers, and microprocessors, which maybe all or part of a central processing unit (CPU), a digital signalprocessor (DSP), a field programmable gate array (FPGA), or any othercircuit known to those skilled in the art that may be suitable forexecuting instructions or performing logic operations.

FIG. 3 illustrates that the external unit 120 may further be associatedwith a power source 140. The power source may be removably couplable tothe external unit at an exterior location relative to external unit.Alternatively, as shown in FIG. 3, power source 140 may be permanentlyor removably coupled to a location within external unit 120. The powersource may further include any suitable source of power configured to bein electrical communication with the processor. In one embodiment, forexample the power source 140 may include a battery.

The power source may be configured to power various components withinthe external unit 120. As illustrated in FIG. 3, power source 140 may beconfigured to provide power to the processor 144. In addition, the powersource 140 may be configured to provide power to a signal source 142 anda feedback circuit 148. The signal source 142 may be in communicationwith the processor 144 and may include any device configured to generatea signal (e.g., a sinusoidal signal, square wave, triangle wave,microwave, radio-frequency (RF) signal, or any other type ofelectromagnetic signal). Signal source 142 may include, but is notlimited to, a waveform generator that may be configured to generatealternating current (AC) signals and/or direct current (DC) signals, inone embodiment, for example, signal source 142 may be configured togenerate an AC signal for transmission to one or more other components.Signal source 142 may be configured to generate a signal of any suitablefrequency. In some embodiments, signal source 142 may be configured togenerate a signal having a frequency of from about 6.5 MHz to about 13.6MHz. In additional embodiments, signal source 142 may be configured togenerate a signal having a frequency of from about 7.4 to about 8.8 MHz.In further embodiments, signal source 142 may generate a signal having afrequency as low as 90 kHz or as high as 28 MHz.

Signal source 142 may be configured for direct or indirect electricalcommunication with an amplifier 146. The amplifier may include anysuitable device configured to amplify one or more signals generated fromsignal source 142. Amplifier 146 may include one or more of varioustypes of amplification devices, including, for example, transistor baseddevices, operational amplifiers, RF amplifiers, power amplifiers, or anyother type of device that can increase the gain associated with one ormore aspects of a signal. The amplifier may further be configured tooutput the amplified signals to one or more components within externalunit 120.

Feedback circuit 148, as shown in FIG. 3, may be in electricalcommunication with various components of external unit 120. For example,feedback circuit 148 may be in direct or indirect electrical contactwith processor 144 and a primary antenna 150. In some embodiments,feedback circuit 145 may include, for example, a signal analyzer or adetector.

The external unit 120 may additionally include primary antenna 150. Asshown in FIG. 3, primary antenna 150 may be configured as part of acircuit within external unit 120 and may be coupled either directly orindirectly to various components in external unit 120. For example, asshown in FIG. 3, primary antenna 150 may be configured for communicationwith the amplifier 146.

The primary antenna 150 may include any conductive structure that may beconfigured to create an electromagnetic field. The primary antenna 150may further be of any suitable size, shape, and/or configuration. Thesize, shape, and/or configuration may be determined by the size of thepatient, the placement location of the implant unit, the size and/orshape of the implant unit, the amount of energy required to modulate anerve, a to of a nerve to be modulated, the type of receivingelectronic's present on the implant unit, etc. The primary antenna mayinclude any suitable antenna known to those skilled in the art that maybe configured to send and/or receive signals. Suitable antennas mayinclude, but are not limited to, a to antenna, a patch antenna, ahelical antenna, etc. In one embodiment, for example, as illustrated inFIG. 3, primary antenna 150 may include a coil antenna. Such a coilantenna may be made from any suitable conductive material and may beconfigured to include any suitable arrangement of conductive coils(e.g., diameter, number of coils, layout of coils, etc.). A coil antennasuitable for use as primary antenna 150 may have a diameter of betweenabout 1 cm and 10 cm, and may be circular or oval shaped, in someembodiments, a coil antenna may have a diameter between 5 cm and 7 cm,and may be oval shaped. A coil antenna suitable for use as primaryantenna 150 may have any number of windings, e.g. 4, 8, 12, or more. Acoil antenna suitable for use as primary antenna 150 may have a wirediameter between about 0.01 mm and 2 mm. These antenna parameters areexemplary only, and may be adjusted above or below the ranges given toachieve suitable results.

As noted, implant unit 110 may be configured to be implanted in apatient's body (e.g., beneath the patient's skin). FIG. 2 illustratesthat the implant unit 110 may be configured to be implanted formodulation of a nerve associated with a muscle of the subject's tongue130. Modulating a nerve associated with a muscle of the subject's tongue130 may include stimulation to cause a muscle contraction, in furtherembodiments, the implant unit may be configured to be placed inconjunction with any nerve that one may desire to modulate. For example,modulation of the occipital nerve, the greater occipital nerve, and/orthe trigeminal nerve may be useful for treating pain sensation in thehead, such as that from migraines. Modulation of parasympathetic nervefibers on and around the renal arteries. (i.e., the renal nerves), thevagus nerve, and/or the glossopharyngeal nerve may be useful fortreating hypertension. Additionally, any nerve of the peripheral nervoussystem (both spinal and cranial), including motor neurons, sensoryneurons, sympathetic neurons and parasympathetic neurons, may bemodulated to achieve a desired effect.

Implant unit 110 may be formed of any materials suitable forimplantation into the body of a patient. In some embodiments, implantunit 110 may include a flexible carrier 161 FIG. 4) including aflexible, biocompatible material. Such materials may include, forexample, silicone, polyimides, phenyltrimethoxysilane (PTMS), polymethylmethacrylate (PMMA), Parylene C, polyimide, liquid polyimide, laminatedpolyimide, black epoxy, polyether ether ketone (PEEK), Liquid CrystalPolymer (LCP), Kapton, etc. Implant unit 110 may further includecircuitry including conductive materials, such as gold, platinum,titanium, or any other biocompatible conductive material or combinationof materials. Implant unit 110 and flexible carder 161 may also befabricated with a thickness suitable for implantation under a patient'sskin. Implant 110 may have thickness of less than about 4 mm or lessthan about 2 mm. Other components that may be included in or otherwiseassociated with the implant unit are illustrated in FIG. 3. For example,implant unit 110 may include a harmonics modifier circuit 154,non-linear circuit components, such as diode 156, and a secondaryantenna 152 mounted onto or integrated with flexible carder 161.Harmonics modifier circuit 154 may include any electrical componentsconfigured to non-linearly after the harmonics generated in implant unit110. Similar to the primary antenna 150, the secondary antenna 152 mayinclude any suitable antenna known to those skilled in the art that maybe configured to send and/or receive signals. The secondary antenna mayinclude any suitable size, shape, and/or configuration. The size, shapeand/or configuration may be determined by the size of the patient, theplacement location of the implant unit, the amount of energy required tomodulate the nerve, etc. Suitable antennas may include, but are notlimited to, a long-wire antenna, a patch antenna, a helical antenna,etc. In some embodiments, for example, secondary antenna 152 may includea coil antenna having a circular shape (see also FIG. 4) or oval shape.Such a coil antenna may be made from any suitable conductive materialand may be configured to include any suitable arrangement of conductivecoils (e.g., diameter, number of coils, layout of coils, etc.). A coilantenna suitable for use as secondary antenna 152 may have a diameter ofbetween about 5 mm and 30 mm, and may be circular or oval shaped. A coilantenna suitable for use as secondary antenna 152 may have any number ofwindings, e.g. 4, 15, 20, 30, or 50. A coil antenna suitable for use assecondary antenna 152 may have a wire diameter between about 0.001 mmand 1 mm. These antenna parameters are exemplary only, and may beadjusted above or below the ranges given to achieve suitable results.FIGS. 11a and 11b illustrate a double-layer crossover antenna 1101suitable for use as either prima antenna 150 or secondary antenna 152.While a double-layer crossover antenna is shown and described, otherantenna configurations may be suitable for primary antenna 150 and/orsecondary antenna 152. For example, single layer antennas may be usedwhere antenna components (e.g., coils) are arranged in a single layer,e.g., either on or within a dielectric or insulating material. Also,while a crossover pattern is shown, other patterns may also be suitable.For example, in some embodiments, a wire associated with primary antenna150 and/or secondary antenna 152 may include a pattern of traces ofprogressively decreasing dimension. In the case of traces arranged incoils, for example, each loop may include rings of progressivelydecreasing diameter to create a pattern that spirals inwardly. A similarapproach may be viable using traces of other shapes as well.

Returning to FIG. 11a , this figure illustrates a single coil ofdouble-layer crossover antenna 1101, while FIG. 11b illustrates twolayers of double layer crossover antenna 1101. Antenna 1101 may includea first coil of wire 1102 arranged on a first side of a dielectriccarrier 1104 and a second coil of wire 1103 on a second side of adielectric carrier 1104.

Arranging the antenna coils in a double layer may serve to increase thetransmission range of the antenna without increasing the size of theantenna. Such an arrangement, however, may also serve to increasecapacitance between the wires of each coil. In each wire coil, an amountof parasitic capacitance between wires may partially depend on thedistance each wire is from its neighbor. In a single layer coil,capacitance may be generated between each loop of the coil and itsneighbors to either side. Thus, more compact coils may generate moreparasitic capacitance. When a second layer coil is added, additionalcapacitance may then be generated between the wires of the first coiland the wires of the second coil. This additional capacitance may befurther increased if corresponding loops of the first and second coilshave the same or similar diameters, and/or if a dielectric carrierseparating the bops is made very thin. Increased parasitic capacitancein an antenna may serve to after characteristics, such as resonantfrequency, of the antenna in unpredictable amounts based onmanufacturing specifications. Additionally, resonant frequency drift,caused for example by moisture incursion or antenna flexing, may beincreased by the presence of increased parasitic capacitance. Thus, inorder to decrease variability in the manufactured product, it may beadvantageous to reduce the levels of parasitic capacitance in a duallayer antenna.

FIG. 11b illustrates a double layer crossover antenna 1101 which mayserve to reduce the parasitic capacitance in a manufactured antenna. Asillustrated in FIG. 11b , a first coil of wire 1102 is concentricallyoffset from a second coif of wire 1103. In contrast to a configurationwhere each loop of a first coil 1102 has the same diameter ascorresponding loop of the second coil 1103, concentrically offsettingcorresponding loops of each wire coil serves to increase the distancebetween a single loop of the first coil 1102 with a corresponding loopof the second coil 1103. This increased distance, in turn, may decreasethe parasitic wire-to-wire capacitance between loops of first coil 1102and corresponding loops of second coil 1103. This configuration may beparticularly advantageous in reducing parasitic capacitance in asituation where a dielectric carrier 1104 is thin enough such that theconcentric distance by which each coil is offset is relatively largecompared to the thickness of the dielectric carrier 1104. For example,in a situation where a dielectric carrier is 0.5 mm thick, a concentricoffset of 0.5 mm or more may produce a large change in parasiticcapacitance. In contrast, in a situation where a dielectric carrier is 5mm thick, a concentric offset of 0.5 mm may produce a smaller change inparasitic capacitance. The concentric offset between a first coil 1102and a second coil 1103 may be achieved, for example, by a plurality ofelectrical trace steps 1105 that offset each loop of the coils from eachpreceding loop. Electrical trace steps 1105 on a first side ofdielectric carrier 1104 cross over electrical trace steps 1105 on asecond side of dielectric earner 1104, thus providing the crossoverfeature of double-layer crossover antenna 1101.

In additional embodiments, double layer crossover antenna 1101 mayinclude openings 1106 in dielectric carrier 1104 to facilitate theelectrical connection of first and second coils 1102, 1103. For example,one or more conductive wires, vies, traces, etc. may extend throughopenings 1106 in dielectric carrier 1104 in order to establishelectrical connectivity between the first and second coils 1102, 1103.First and second coifs 1102, 1103 of double layer crossover antenna 1101may also include exposed electrical portions 1108 configured toelectrically connect with a connector of a device housing that may becoupled to antenna 1101. Exposed electrical portions 1108 may beconfigured so as to maintain electrical contact with the connector of adevice housing independent of the axial orientation of the connection,as discussed further below.

As shown in FIG. 11c , exposed electrical portions 1108 may beconfigured in a pattern suitable for maintaining electrical contact withcorresponding electrodes on an external unit 120, for example. In someembodiments, exposed electrical portions 1108 may be arranged in or maycomprise continuous or discontinuous patterns of conductive materialassociated with carrier 1104. For example, exposed electrical portions1108 may be arranged in continuous or discontinuous circles, ellipses,polygons, or any other suitable shape. In some embodiments, exposedelectrical portions 1108 may include a first exposed electrical portion1108 a, forming a discontinuous circle, and a second exposed electricalportion 1108 b, forming a continuous circle and located inside firstexposed electrical portion 1108 a, in some embodiments, first electricalelectrical portions 1108 a may form an arc shape. Exposed electricalportion 1108 may include a plurality of first and second electricalelectrical portions 1108 a, 1108 b (respectively), for example, 1, 2, 4,or 5 of each. Additionally, exposed electrical portion 1108 may includean unequal number of first exposed electrical portions 1108 a and secondexposed electrical portions 1108 b. For example, a greater number offirst exposed electrical portions 1108 a may be included as compared tosecond exposed electrical portions 1108 b.

First exposed electrical portion 1108 a may form a C-shape or U-shapeconfiguration, providing a space 1109 between open ends. As shown inFIG. 11c , space 1109 may be configured for an electrical trace to passthrough without contacting first exposed electrical portion 1108 a. Forexample, space 1109 may allow the electrical trace to connect withsecond exposed electrical portion 1108 b, or to other components locatedwithin the circle of first exposed electrical portion 1108 a.

FIG. 11c illustrates an exposed electrical portion 1108 withsubstantially circular first and second exposed electrical portions 1108a, 1108 b. However, it is further contemn plated that other shapes maybe utilized, for example, elliptical, triangular, square, etc.Additionally, although antenna 1101 is shown in FIG. 11a withsubstantially elliptical coils, other shapes, such as circular,triangular, square, etc., may be also be used in different embodiments.Elliptical coils may facilitate placement of external unit 120 incertain areas (e.g., under the chin of a subject) while, maintainingdesirable electrical performance characteristics.

FIGS. 12a and 12b illustrate an exemplary embodiment of external unit120, including features that may be found in any combination in otherembodiments. FIG. 12a illustrates a side view of external unit 120,depicting carrier 1201 and electronics housing 1202.

Housing 1202 may be configured to contain various electrical andmechanical components, as discussed above with respect to FIG. 3.Housing 1202 may include a bottom surface 1250, a top surface 1252, andat least one sidewall 1251. When configured in a generally cylindricalarrangement, sidewall 1251 may be a continuous surface. Bottom surface1250 may be configured to contact carrier 1201.

Carrier 1201 may include a skin patch configured for adherence to theskin of a subject, and having a first side 1241 and a second side 1242.Carrier 1201 may be flexible or rigid, or may have flexible portions andrigid portions. A securing element 1250 may be disposed on the firstside 1241 of carder 1201. Securing element 1250 may include achemical-based agent (e.g., an adhesive material) or mechanicalstructures configured to secure carder 1201 to a patient (e.g., to thepatient's skin). In some embodiments, securing element 1240 may includean adhesive, a bonding material, a strap, or any suitable fastener. Asshown in FIG. 12a , securing element 150 may be disposed along theentire length of first side 1241 or along a portion of first side. Forexample, securing element 1250 may only be disposed along flexibleportions of carder 1201.

Carrier 1201 and may include primary antenna 150, for example, adouble-layer crossover antenna 1101 such as that illustrated in FIGS.11a and 11b . Carrier 1201 may also include power source 140, such as apaper battery, thin film battery, or other type of substantially flatand/or flexible battery. Carrier 1201 may also include any other type ofbattery or power source.

Carrier 1201 may also include a connector 1203 configured forselectively or removably connecting carrier 1201 to electronics housing1202. Connector 1203 may include a mechanical or electrical connection.For example, connector 1203 may include a protrusion extending orprotruding away from second side 1242. As shown in FIG. 12a , connector1203 may form a rod-like extension 1234 configured to mate with areceiver 1204 in electronics housing 1202. Receiver 1204 may include arecess or depression in electronics housing 1202. In some embodiments,connector 1203 and receive 1204 may form an interference fit. One ormore detente 1232 on connector 1203 may engage one or more detentengagement portions 1233 on electronics housing 1202 to secure connector1203 to electronics housing 1202. Alternatively, connector 1203 may forma recess, for example opening 1235 as shown in FIG. 12b . Opening 1235may be configured to engage one or more securing means on electronicshousing 1202 to secure carrier 1201 to electronics housing.

Connector 1203 may include various configurations and dimensions. Forexample, connector 1283 may be configured as a non-pouch connector,configured to provide a selective connection to electronics housing 1204without the substantial use of concave feature. Connector 1203 mayinclude, for example a peg, and may have flexible arms. Connector 1203may further include a magnetic connection, a velcro connection, and/or asnap dome connection. Connector 1203 may also include a locatingfeature, configured to locate electronics housing 1202 at a specificheight, axial location, and/or axial orientation with respect to carrier1201. A locating feature of connector 1203 may further include pegs,rings, boxes, ellipses, bumps, etc.

Connector 1203 may be centered on carrier 1201, may be offset from thecenter by a predetermined amount, or may be provided at any othersuitable location of carrier 1201. Multiple connectors 1203 may beprovided on carrier 1201. Additionally, connector 1203 may be removablefrom electronics housing. In some embodiments, connector 1203 may beconfigured such that removal from electronics housing 1202 may causebreakage of connector 1203. This may prevent re-use of carrier 1201,which may be desirable when carder 1201 loses efficacy through continueduse.

Electronics housing 1202 is illustrated in side view in FIG. 12a and ina bottom view in FIG. 12b . Electronics housing 1202 may be disposed onsecond side 1242 of carder 1201, and may include electronics portion1205, arranged inside electronics housing 1202 in any manner that issuitable. Electronics portion 1205 may include various components,further discussed below, of external unit 120. For example, electronicsportion 1205 may include any combination of at least one processor 144associated with external unit 120, power source 140, such as a battery,primary antenna 150, and an electrical circuit 170 (as shown in FIG. 6).Electronics portion 1205 may also include any other component describedherein as associated with external unit 120. Additional components mayalso be recognized by those of skill in the art.

Electronics housing 1202 may include at least one electrical connector1210, 1211, 1212. Electrical connectors 1210, 1211, 1212 may be arrangedwithin pairs of electrical contacts 1215, as shown in FIG. 12b , or withany other number of electrical contacts. The pair of electrical contacts1215 of each electrical connector 1210, 1211, 1212 may be continuouslyelectrically connected with each other inside of housing 1202, such thatthe pair of electrical contacts 1215 represents a single connectionpoint to a circuit, in such a configuration, it is only necessary thatone of the electrical contacts within a pair be connected to thecircuit. Electrical connectors 1210, 1211, 1212 may thus includeredundant electrical contacts. The electrical contacts of eachelectrical connector 1210, 1211, 1212 may also represent opposite endsof a circuit, for example, the positive and negative ends of a batterycharging circuit.

In an exemplary embodiment, electronics housing 1202 and carrier 1201may be configured to maintain electrical contact independent of an axialorientation of housing 1202 with respect to carrier 1201. Therefore,when housing 1202 is mated with and secured to carrier 1201, forexample, through connector 1203 and receiver 1204, housing 1202 may beconfigured to rotate with respect to carrier 1201 while maintainingelectrical contact between housing 1202 and carrier 1201. Housing 1202may be configured to rotate a predetermined degree of rotation whilemaintaining electrical contact. The predetermined degree of rotation mayinclude, for example, about 360 degrees, more than about 360 degrees, oran angle less than 360 degrees (e.g. about 180 degrees, about 90degrees, or about 45 degrees). Additionally, housing 1202 may beconfigured to rotate upwards or downwards with respect to carrier 1201.For example, a left side of sidewall 1251 may rotate upward and awayfrom carrier 1201 while a right side of sidewall 1251 may rotatedownward and toward carrier 1201, while still maintaining electricalcontact between housing 1202 and carrier 1201. It is furthercontemplated that carder 1201 may be configured to rotate with respectto housing 1201.

Rotation of housing 1201 and/or carder 1201, while maintainingelectrical contact between the components, may be accomplished throughconnectors 1210, 1211, 1212 on housing 1202 and exposed electricalportions 1108 on carder 1201. As shown in FIG. 12b , electricalconnectors 1210, 1211, and 1212 may be configured so as to maintainelectrical contact with exposed electrical portions 1108, on carder1201, independent of an axial orientation of electronics housing 1202.Connection between any or all of electrical connectors 1210, 1211, 1212and exposed electrical portions 1108 may thus be established andmaintained irrespective of relative axial positions of carder 1201 andhousing 1202. Thus, when connector 1203 is mated with receiver 1204,housing 1202 may rotate with respect to carrier 1201 withoutinterrupting electrical contact between at least one of electricalconnectors 1210, 1211, 1212 and exposed electrical portions 1108.

Electrical connectors 1210, 1211, 1212, may be arranged in apredetermined pattern with respect to exposed electrical portions 1108to achieve the axial orientation independence of housing 1202 and carder1201. For example, the pairs of electrical contacts 1215 may be disposedequidistant from a center C of bottom surface 1250 of housing 1202 (FIG.12b ). In some embodiments, the pairs of electrical contacts 1215 may bedisposed equidistant from a center of receiver 1204. This arrangement ofthe pairs of electrical contacts 1215 may allow electrical connectors1210, 1211, 1212 to be equally spaced from the center as electricalconnectors 1210, 1211, 1212 on a corresponding electrical contact 1215.For example, as shown in FIG. 12b , an outer connector 1210 on a firstelectrical contact 1215 is disposed at a distance from the center Cequal to a distance from the center C where outer connector 1210 on asecond (or other) electrical contact 1215 is located. In such aconfiguration, as housing 1202 rotates relative to carrier 1201, atleast one electrode from one or more of the pairs of electrodes 1210,pairs 1211, and pairs 1212 may remain in electrical contact withrespective electrodes or electrical portions associated with housing1202.

The electrical connectors 1210, 1211, 1212 may be disposed a distancefrom center C substantially equal to the radius of a correspondingexposed electrical portion 1108. For example, electrical connector 1210may be disposed a distance equal to the radius R1 of first exposedelectrical portion 1108 a (FIG. 11c ). Therefore, electrical connector1210 may be disposed substantially directly over first exposedelectrical portion 1108 a. Additionally, electrical connector 1211 maybe disposed a distance equal to the radius R2 of second exposedelectrical portion 1108 b, and therefore substantiality over secondexposed electrical portion 1108 b. Each of electrical connectors 1210,1211, 1212 may make contact with its corresponding exposed electricalportion 1108. Therefore, first exposed electrical portion 1108 a may bein electrical contact with electrical connector 1210, and second exposedelectrical portion 1108 b may be in electrical contact with connector1211. When exposed electrical portions 1108 include a discontinuouscircle, such as first exposed electrical portion 1108 a, therebysubstantially preventing electrical contact between first exposedelectrical portion 1108 a and its corresponding electrical connector1210, electrical contact between housing 1202 and carrier 1201 may stillbe maintained between second exposed electrical portion 1108 b andelectrical connector 1211.

In other embodiments, electrical connectors 1210, 1211, 1212 may makecontact with an offset exposed electrical portion 1108. For example,continuing the above example, electrical connector 1212 may be offsetfrom second electrical portion 1108 b, but still configured to makeelectrical contact with second electrical portion 1108 b. Therefore,when housing 1202 includes more electrical connectors than there areexposed electrical portions 1108, each electrical connector may be incontinuous electrical contact with carrier 1201. Housing 1202 mayinclude any number of electrical connectors with regard to the number ofexposed electrical portions 1108 on carrier 1201.

When in electrical contact with electrical connectors 1210, 1211, 1212,exposed electrical portions 1108 may also be electrically connected tothe electrical components contained in electronics portion 1205.However, in some embodiments, electrical connectors 1210, 1211, 1212 maybe used in configurations not involving contact with electrodes oncarder 1201. In such embodiments, for example, electrical connectors1210, 1211, 1212 may be configured to function as opposite ends of abattery charging circuit and may be configured and used to charge abattery contained in electronics portion 1205.

As shown in FIG. 12b , electrical connectors 1210, 1211, 1212 areillustrated as substantially rectangular. However, electrical connectors1210, 1211, 1212 may include a variety of shapes and configurations. Forexample, these electrical connectors may be circular, elliptical,triangular, square, etc. In some embodiments, electrical connectors1210, 1211, 1212 may be configured as continuous or discontinuouspatterns (e.g., circular patterns or patterns of any other suitableshape). It is further contemplated that housing 1202 may include anysuitable number of connectors.

In an additional embodiment consistent with the present disclosure,electronics housing 1202 may include an activator chip. Processor 144may be configured to activate when at least one of electrical connectors1210, 1211, 1212 contact exposed electrical portions 1108 included incarrier 1201. In this manner, an electronics housing 1202 may be chargedand left dormant for many days prior to activation. Simply connectingelectronics housing 1202 to carrier 1201 (and inducing contact betweenan electrical connector 1210, 1211, 1212 and an electrical portion 1108)may cause the processor to activate. Upon activation, processor 144 maybe configured to enter a specific mode of operation, such as acalibration mode (for calibrating the processor after placement of thecarrier on the skin), a placement mode (for assisting a user to properlyplace the carrier on the skin), and/or a therapy mode (to begin atherapy session). The various modes of processor 144 may include waitingperiods at the be end, or at any time during. For example, a placementmode may include a waiting period at the end of the mode to provide aperiod during which a subject may fall asleep. A therapy mode mayinclude a similar waiting period at the beginning of the mode.Additionally or alternatively, processor 144 may be configured toprovide waiting periods separate from the described modes, in order toprovide a desired temporal spacing between system activities. Implantunit 110, as shown in FIG. 3, may additionally include a plurality offield-generating implant electrodes 158 a, 158 b. The electrodes mayinclude any suitable shape and/or orientation on the implant unit solong as the electrodes may be configured to generate an electric fieldin the body of a patient. Implant electrodes 158 a and 158 b may alsoinclude any suitable conductive material (e.g., copper, silver, gold,platinum, iridium, platinum-iridium, platinum-gold, conductive polymers,etc.) or combinations of conductive (and/or noble metals) materials. Insome embodiments, for example, the electrodes may include short lineelectrodes, circular electrodes, and/or circular pairs of electrodes. Asshown in FIG. 4, electrodes 158 a and 158 b may be located on an end ofa first extension 162 a of an elongate arm 162. The electrodes, however,may be located on any portion of implant unit 110. Additionally, implantunit 110 may include electrodes 158 a, 158 b located at a plurality oflocations, for example on an end of both a first extension 162 a and asecond extension 162 b of elongate arm 162, as illustrated, for example,in FIG. 5. Implant electrodes 156 a, 158 b may have a thickness betweenabout 200 nanometers and 1 millimeter. Anode and cathode electrode pairsof electrodes 158 a, 158 b may be spaced apart by about a distance ofabout 0.2 mm to 25 mm. In additional embodiments, anode and cathodeelectrode pairs may be spaced apart by a distance of about 1 mm to 10mm, or between 4 mm and 7 mm. Adjacent anodes or adjacent cathodes maybe spaced apart by distances as small as 0.001 mm or less, or as greatas 25 mm or more. In some embodiments, adjacent anodes or adjacentcathodes may be spaced apart by a distance between about 0.2 mm and 1mm.

FIG. 4 provides a schematic representation of an exemplary configurationof implant unit 110. As illustrated in FIG. 4, in one embodiment, thefield-generating electrodes 158 a and 158 b may include two sets of fourcircular electrodes, provided on flexible carrier 161, with one set ofelectrodes providing an anode and the other set of electrodes providinga cathode. Implant unit 110 may include one or more structural elementsto facilitate implantation of implant unit 110 into the body of apatient. Such elements may include, for example, elongated arms, sutureholes, polymeric surgical mesh, biological glue, spikes of flexiblecarrier protruding to anchor to the tissue, spikes of additionalbiocompatible material for the same purpose, etc. that facilitatealignment of implant unit 110 in a desired orientation within apatient's body and provide attachment points for securing implant unit110 within a body. For example, in some embodiments, implant unit 110may include an elongate arm 162 having a first extension 162 a and,optionally, a second extension 162 b. Extensions 162 a and 162 b may aidin orienting implant unit 110 with respect to a particular muscle (e.g.,the genioglossus muscle), a nerve within a patient's body, or a surfacewithin a body above a nerve. For example, first and second extensions162 a, 162 b may be configured to enable the implant unit to conform atleast partially around soft or hard tissue (e.g., nerve, bone, ormuscle, etc.) beneath a patient's skin. Further, implant unit 110 mayalso include one or more suture holes 160 located anywhere on flexiblecarrier 161. For example, in some embodiments, suture holes 160 may beplaced on second extension 162 b of elongate arm 162 and/or on firstextension 162 a of elongate arm 162. Implant unit 110 may be constructedin various shapes. Additionally, or alternatively, implant unit 110 mayinclude surgical mesh 1050 or other perforatable material, described ingreater detail below with respect to FIG. 10. In some embodiments,implant unit may appear substantially as illustrated in FIG. 4. In otherembodiments, implant unit 110 may lack illustrated structures such assecond extension 162 b, or may have additional or different structuresin different orientations. Additionally, implant unit 110 may be formedwith a generally triangular, circular, or rectangular shape, as analternative to the winged shape shown in FIG. 4. In some embodiments,the shape of implant unit 110 (e.g., as shown in FIG. 4) may facilitateorientation of implant unit 110 with respect to a particular nerve to bemodulated. Thus, other regular or irregular shapes may be adopted inorder to facilitate implantation in differing parts of the body.

As illustrated in FIG. 4, secondary antenna 152 and electrodes 158 a,158 b may be mounted on or integrated with flexible carder 161. Variouscircuit components and connecting wires (discussed further below) may beused to connect secondary antenna with implant electrodes 158 a and 158b. To protect the antenna, electrodes, circuit components, andconnecting wires from the environment within a patient's body, implantunit 110 may include a protective coating that encapsulates implant unit110. In some embodiments, the protective coating may be made from aflexible material to enable bending along with flexible carrier 181. Theencapsulation material of the protective coating may also resisthumidity penetration and protect against corrosion. In some embodiments,the protective coating may include a plurality of layers, includingdifferent materials or combinations of materials in different layers

FIG. 5 is a perspective view of an alternate embodiment of an implantunit 110, according to an exemplary embodiment of the presentdisclosure. As illustrated in FIG. 5, implant unit 110 may include aplurality of electrodes 158 a, 158 b located, for example, at the endsof first extension 162 a and second extension 182 b. FIG. 5 illustratesan embodiment wherein implant electrodes 158 a and 158 b include shortline electrodes. FIG. 10 is a photograph illustrating additionalfeatures of one embodiment of implant unit 110. Exemplary embodimentsmay incorporate some or all of the features illustrated in FIG. 10. Aprotective coating of implant unit 110 may include a primary capsule1021. Primary capsule 1021 may encapsulate the implant unit 110 and mayprovide mechanical protection for the implant unit 110. For example, thecomponents of implant unit 110 may be delicate, and the need to handlethe implant unit 110 prior to implantation may require additionalprotection for the components of implant unit 110. Primary capsule 1021may provide such protection. Primary capsule 1021 may encapsulate, allor some of the components of implant unit 110. For example, primarycapsule 1021 may encapsulate primary antenna 152, carrier 161, andcircuit 180, while leaving electrodes 158 a, 158 b exposed. Inalternative embodiments, different combinations of components may beencapsulated or exposed. Primary capsule 1021 may be fashioned of amaterial and thickness such that implant unit 110 remains flexible afterencapsulation. Primary capsule 1021 may include any suitablebio-compatible material, such as silicone, or polyimides,phenyltrimethoxysilane (PTMS), polymethyl methacrylate (PMMA), ParyleneC, liquid polyimide, laminated polyimide, polyimide, Kapton, blackepoxy, polyether ketone (PEEK), Liquid Crystal Polymer (LCP), or anyother suitable biocompatible coating.

The protective coating of implant unit 110 may also include a secondarycapsule (not shown). A secondary capsule may provide environmentalprotection for the implant unit 110 when it is implanted in the body.For example, primary capsule 1021, when constructed of silicone, may besubject to moisture incursion from the body, which may limit a life-spanof the implant unit 110 due to possible corrosive effects. A secondarycapsule may be provided underneath the primary capsule to protectimplant unit 110 from the corrosive effects of bodily implantation. Forexample, a layer of parylene C may serve as a secondary capsule and maybe provided to encapsulate all or some of the components of implant unit110. The secondary capsule may, in turn, be encapsulated by primarycapsule 1021. A secondary capsule, may include, for example parylene Cor any other suitable material to prevent the effects of moistureincursion on implant unit 110. In some embodiments, a secondary capsulelayer may be deposited by chemical vapor deposition and may have athickness of about 1 molecule in thickness, between 1 and 5 molecules inthickness, or any other suitable film thickness.

Some combinations of primary and secondary capsule materials, such assilicone and parylene C, may bond relatively weakly to one another.Where such combinations of materials are used, a plurality penetratingholes 1030 may be provided to pass through both carrier 161 and asecondary capsule to improve the adherence of the primary capsule. Whenpenetrating holes 1030 are provided, the material of primary capsule1021 may flow through the penetrating holes, permitting the material ofprimary capsule 1021 to flow into and adhere to itself. A plurality ofpenetrating holes 1030 provided through carrier 161 and a secondarycapsule may provide a multitude of anchor points to permit a primarycapsule 1021 material to self adhere. Penetrating holes 1030 may beprovided such that, after encapsulation by primary capsule 1021, theholes 1030 remain, or they may be provided such that, afterencapsulation, the holes 1030 are filled in.

Also illustrated in FIG. 10 is encapsulated surgical mesh 1050. Surgicalmesh 1050 may provide a larger target area for surgeons to use whensuturing implant unit 110 into place during implantation. The entiresurgical mesh 1050 may be encapsulated by primary capsule 1021,permitting a surgeon to pass a needle through any portion of the meshwithout compromising the integrity of implant unit 110. Surgical mesh1050 may additionally be used to cover suture holes 160, permittinglarger suture holes 160 that may provide surgeons with a greater targetarea. Surgical mesh 1050 may also encourage surrounding tissue to bondwith implant unit 110. In some embodiments, a surgeon may pass asurgical suture needle through suture holes 160, located on oneextension 162 a of an elongate arm 162 of implant unit 110, throughtissue of the subject, and through surgical mesh 1050 provided on asecond extension 162 b of elongate arm 162 of implant unit 110. In thisembodiment, the larger target area provided by surgical mesh 1050 mayfacilitate the suturing process because it may be more difficult toprecisely locate a suture needle after passing it through tissue.Implantantation and suturing procedures may be further facilitatedthrough the use of a delivery tool, described in greater detail below.The capsules of implant unit 110 may be provided such that implant unit110 remains flexible after encapsulation. Additionally, implant unit 110may include meandering electrical traces 1060 in order to maintainelectrical contact under flexural conditions. As used herein, meanderingelectrical traces 1060 may include any electrical trace that is longerthan the shortest distance between the points that it connects.Meandering electrical traces 1060 may also include any trace ofsufficient length so as to maintain electrical conductivity duringflexing of a carrier on which it is located. For example, as shown inFIG. 10, meandering electrical traces 1060 may be configured as lineshaving successive curves, such as waves or the like. Repeated flexing ofcarrier 161 on which electrical traces are deposited may causedegradation of the electrical traces, as they are repeatedly stressedwith the flexure of carrier 161. Meandering electrical traces 1060 mayprovide an increased lifetime as the additional sack provided may serveto reduce stress in the traces during flexing of carder 161. Meanderingelectrical traces 1060 may include any suitable conductive material,such as gold, platinum, titanium, copper, silver, iridium,platinum-iridium, platinum-gold, conductive polymers, any conductivebiocompatible material, and/or combinations of conductive (and/or noblemetals) materials.

In additional embodiments consistent with the present disclosure,conductive electrical elements of implant unit 110, such as meanderingtraces 1060 and electrodes 158 a, 158 b may be provided through aprogressive metallization layering method. In some embodiments, flexiblecarder 161 may include a material, such as liquid crystal polymer, thatbonds relatively weakly to conductive metals desirable for use asconductive electrical elements, such as titanium and/or gold. Aprogressive metallization layering method may utilize a temporarybonding layer, including a metal, such as nickel, that may bond morestrongly to flexible carder 161. The temporary bonding layer may belayered with the metals desirable for use as conductive electricalelements and used to provide an initial bond with the material offlexible carder 161. The temporary bonding layer may then be removedthrough dissolution, erosion, or similar technique, through flexiblecarrier 161, leaving the desirable metals in place in flexible carrier161.

In one embodiment, a progressive metallization layering method may beutilized to provide gold and titanium conductive elements on a liquidcrystal polymer carder 161. The conductive elements may be constructedfrom progressive layers of nickel, gold, and titanium. Next, liquidcrystal polymer may be molded around the conductive elements, bondingstrongly with the nickel layer and forming a recess containing thelayered conductive element. Finally, the nickel may be removed throughthe liquid crystal polymer through dissolution, erosion, or similartechnique. The removal of nickel leaves the gold/titanium layeredconductive element in place, held tightly in the liquid crystal polymerrecess created during the molding process.

Returning to FIGS. 2 and 3, external unit 120 may be configured tocommunicate with implant unit 110. For example, in some embodiments, aprimary signal may be generated on primary antenna 150, using, e.g.,processor 144, signal source 142, and amplifier 146. More specifically,in one embodiment, power source 140 may be configured to provide powerto one or both of the processor 144 and the signal source 142. Theprocessor 144 may be configured to cause signal source 142 to generate asignal (e.g., an RF energy signal). Signal source 142 may be configuredto output the generated signal to amplifier 146, which may amplify thesignal generated by signal source 142. The amount of amplification and,therefore, the amplitude of the signal may be controlled, for example,by processor 144. The amount of gain or amplification that processor 144causes amplifier 146 to apply to the signal may depend on a variety offactors, including, but not limited to, the shape, size, and/orconfiguration of primary antenna 150, the size of the patient, thelocation of implant unit 110 in the patient, the shape, size, and/orconfiguration of secondary antenna 152, a degree of coupling betweenprimary antenna 150 and secondary antenna 152 (discussed further below),a desired magnitude of electric field to be generated by implantelectrodes 158 a, 158 b, etc. Amplifier 146 may output the amplifiedsignal to primary antenna 150.

External unit 120 may communicate a primary signal on primary antenna150 to the secondary antenna 152 of implant unit 110. This communicationmay result from coupling between primary antenna 150 and secondaryantenna 152. Such coupling of the primary antenna 150 and the secondaryantenna 152 may include any interaction between the primary antenna 150and the secondary antenna 152 that causes a signal on the secondaryantenna 152 in response to a signal applied to the primary antenna 150.In some embodiments, coupling between the primary and secondary antennas150, 152 may include capacitive coupling, inductive coupling,radiofrequency coupling, etc. and any combinations thereof.

Coupling between primary antenna 150 and secondary antenna 152 maydepend on the proximity of the primary antenna 150 relative to thesecondary antenna 152. That is, in some embodiments, an efficiency ordegree of coupling between primary antenna 150 and secondary antenna 152may depend on the proximity of the primary antenna 150 to the secondaryantenna 152. The proximity of the primary and secondary antennas 150,152 may be expressed in terms of a coaxial offset (e.g., a distancebetween the primary and secondary antennas when central axes of theprimary and secondary antennas are co-aligned), a lateral offset (e.g.,a distance between a central axis of the primary antenna and a centralaxis of the secondary antenna), and/or an angular offset (e.g., anangular difference between the central axes of the primary and secondaryantennas). In some embodiments, a theoretical maximum efficiency ofcoupling may exist between primary antenna 150 and secondary antenna 152when both the coaxial offset, the lateral offset, and the angular offsetare zero. Increasing any of the coaxial offset, the lateral offset, andthe angular offset may have the effect of reducing the efficiency ordegree of coupling between primary antenna 150 and secondary antenna152.

As a result of coupling between primary antenna 150 and secondaryantenna 152, a secondary signal may arise on secondary antenna 152 whenthe primary signal is present on the primary antenna 150. Such couplingmay include inductive magnetic coupling, RF coupling/transmission,capacitive coupling, or any other mechanism where a secondary signal maybe generated on secondary antenna 152 in response to a primary signalgenerated on primary antenna 150. Coupling may refer to any interactionbetween the primary and secondary antennas. In addition to the couplingbetween primary antenna 150 and secondary antenna 152, circuitcomponents associated with implant unit 110 may also affect thesecondary signal on secondary antenna 152. Thus, the secondary signal onsecondary antenna 152 may refer to any and all signals and signalcomponents present on secondary antenna 152 regardless of the source.

While the presence of a primary signal on primary antenna 150 may causeor induce a secondary signal on secondary antenna 152, the couplingbetween the two antennas may also lead to a coupled signal or signalcomponents on the primary antenna 150 as a result of the secondarysignal present on secondary antenna 152. A signal on primary antenna 150induced by a secondary signal on secondary antenna 152 may be referredto as a primary coupled signal component. The primary signal may referto any and all signals or signal components present on primary antenna150, regardless of source, and the primary coupled signal component mayrefer to any signal or signal component arising on the primary antenna150 as a result of coupling with signals present on secondary antenna152. Thus, in some embodiments, the primary coupled signal component maycontribute to the primary signal on primary antenna 150.

Implant unit 110 may be configured to respond to external unit 120. Forexample, in some embodiments, a primary signal generated on primary coil150 may cause a secondary signal on secondary antenna 152, which inturn, may cause one or more responses by implant unit 110. In someembodiments, the response of implant unit 110 may include the generationof an electric field between implant electrodes 158 a and 158 b.

FIG. 6 illustrates circuitry 170 that may be included in external unit120 and circuitry 180 that may be included in implant unit 110.Additional, different, or fewer circuit components may be included ineither or both of circuitry 170 and circuitry 180. As shown in FIG. 6,secondary antenna 152 may be arranged in electrical communication withimplant electrodes 158 a, 158 b, in some embodiments, circuitryconnecting secondary antenna 152 with implant electrodes 158 a and 158 bmay cause a voltage potential across implant electrodes 158 a and 158 bin the presence of a secondary signal on secondary antenna 152. Thisvoltage potential may be referred to as a field inducing signal, as thisvoltage potential may generate an electric field between implantelectrodes 158 a and 158 b. More broadly, the field inducing signal mayinclude any signal (e.g., voltage potential) applied to electrodesassociated with the implant unit that may result in an electric fieldbeing generated between the electrodes.

Energy transfer between primary antenna 150 and secondary antenna 152via the primary signal may be improved when a resonant frequency ofprimary antenna 150 and its associated circuitry 170 matches that ofsecondary antenna 152 and its associated circuitry 180. As used herein aresonant frequency match between two antennas may be characterized bythe proximity of two resonant frequencies to one another. For example, aresonant frequency match may be considered to occur when two resonantfrequencies are within 30%, 20%, 10% 5%, 3%, 1%, 0.5%, 0.1%, or less ofeach other. Accordingly, a resonant frequency mismatch may be consideredto occur when two resonant frequencies do not match. The proximity ofthe two resonant frequencies required to be considered a match maydepend on the circumstances of energy transfer between the two antennas.A resonant frequency match between two antennas may also becharacterized by the of efficiency of energy transfer between theantennas. The efficiency of energy transfer between two antennas maydepend on several factors, one of which may be the degree to which theresonant frequencies of the antennas match. Thus, it all other factorsare held constant, changing the resonant frequency of one antenna withrespect to the other will alter the efficiency of energy transfer. Aresonant frequency match between two antennas may be considered to occurwhen the efficiency of energy transfer is within 50% or greater of amaximum energy transfer when all other factors remain constant. In someembodiments, a resonant frequency match may require energy transferefficiencies of 60%, 70%, 80%, 90%, 95% or greater.

Several embodiments are provided in order to appropriately matchresonant frequencies between a primary signal and a secondary antenna152. Because the secondary antenna 152 is intended for implantation withimplant unit 110, it may be difficult to adjust the resonant frequencyof the antenna during use. Furthermore, due to the possibility ofmoisture incursion into primary capsule 1201 encapsulating implant unit110, implant circuitry 180, and secondary antenna 152, a resonantfrequency of the implant unit 110 may drift after implantation. Otherfactors present during implantation may also influence the frequencydrift of implant unit 110 after implantation. This drifting of theresonant frequency may last for several days to several months afterimplantation before stabilizing. For example, the resonant frequency ofan implant unit 110 may drift from 8.1 kHz to 7.9 kHz. Throughexperimentation or simulation, it may be possible to predict by how muchthe resonant frequency may drift. Thus, using the example above, if along term resonant frequency value of 7.9 kHz is desired, an implantunit 110 may be manufactured with a resonant frequency value of 8.1 kHzprior to implantation.

Resonant frequency values of manufactured implant units 110 may beadjusted during the manufacturing process through the use of at leastone trimming capacitor. In one embodiment, carrier 161 may bemanufactured with all or some of the components of the final implantunit, including, for example, secondary antenna 152, implant circuitry180, modulation electrodes 158 a, 158 b. The resonant frequency of thisassembly may then be measured or otherwise determined. Due to variationsin manufacturing processes and materials, the resonant frequency of eachmanufactured unit may differ. Thus, in order to meet a specificresonance frequency, each implant unit may be adjusted through theaddition of one or more trimming capacitors to the implant circuitry 180prior to encapsulation. In one embodiment, a capacitor may be lasertrimmed to an exact capacitance value before insertion into implantcircuitry 180. In another embodiment, a stock capacitor of known valuemay be inserted into implant circuitry 180. In still another embodiment,a plurality of capacitors may be inserted into implanted circuitry 180to appropriately adjust the resonant frequency of implant unit 110. Sucha plurality of capacitors may include a series of capacitors havingprogressively smaller capacitance values, and a resonant frequency ofthe assembly may be measured after the insertion of each capacitor priorto choosing and inserting the next, in this fashion, implantable circuit180 may include at least one capacitor configured to create apredetermined mismatch between a resonant frequency of implantablecircuit 180 and external circuit 170.

In addition to resonant frequency drift in implant unit 110, a resonantfrequency of primary antenna 152 may be altered due to the applicationof the antenna 152 to the skin of a subject. That is, when primaryantenna 152 is bent to conform to the skin of a subject, the spatialrelationship coils within primary antenna 152 may shift, causing achange in resonant frequency. In order to address this, a processor 144of the external unit may be configured to determine a resonant frequencymismatch between primary antenna 152 and secondary antenna 150, andadjust a resonant frequency of primary antenna 152 in order to reduce oreliminate the resonant frequency mismatch. During transmission of aprimary signal from primary antenna 150 to secondary antenna 152,processor 144 may be configured to determine a resonant frequencymismatch based on a primary coupled signal component present on theprimary antenna 150 due to coupling between primary antenna 152 andsecondary antenna 150. Monitoring a primary coupled signal component bythe processor 144 may provide an indication of transmission efficiency,which may in turn be an indication of resonant frequency mismatch. Theprimary coupled signal component and the interaction between primaryantenna 152 and secondary antenna 150 are explained in greater detailbelow.

Upon determining a resonant frequency mismatch between a primary antenna150 and a secondary antenna 152, processor 144 may adjust the resonantfrequency of a self-resonant transmitter circuit including the primaryantenna to reduce the mismatch. A self-resonant transmitter circuit mayinclude features to permit adjustment of a resonant frequency of thecircuit. Such adjustment may be performed, for example through theselective inclusion and exclusion of at least one capacitor into or outof a self-resonant transmitter circuit. Adding (or subtracting)capacitors to the self-resonant transmitter circuit may cause a changein the resonant frequency of the circuit. In the currently describedembodiment, the self-resonant transmitter circuit may be provided withone or more trim capacitors configured, through processor 144 controlledswitches, for selective inclusion and exclusion. The switches mayinclude, for example, transistors or relays. Thus, processor 144 mayinclude or exclude a capacitor from the self-resonant transmittercircuit by opening or closing a switch associated with the respectivecapacitor. Providing a single capacitor, therefore, permits processor144 to switch the resonant frequency of the self-resonant transmittercircuit between two different values. In an exemplary embodiment, a bankof six capacitors may be provided, permitting processor 144 to switchthe resonant frequency of the self-resonant transmitter circuit between64 (i.e., 2⁶) different values. In alternative embodiments, more orfewer capacitors may be provided for adjusting the resonant frequency ofthe self-resonant transmitter circuit.

In an exemplary embodiment, processor 144 may be configured to switchcapacitors from a capacitor bank into and out of the self-resonanttransmitter circuit during transmission of a primary signal to determinea capacitor combination that changes (e.g., increases) transmissionefficiency and resonant frequency match. In some embodiments, processor144 may be configured to select an optimal combination of capacitors toprovide a best resonant frequency match. In alternative embodiments,processor 144 may be configured to select a combination of capacitorsthat provides a resonant frequency match surpassing a predeterminedthreshold, regardless of whether such combination produces an optimalresonant frequency match.

Resonant frequency matching between primary antenna 150 and secondaryantenna 152 may increase the efficiency of energy transfer between theantennas. In further embodiments processor 144 may be configured toadjust the operation of elements within external unit 120 to match afrequency of a primary signal with a resonant frequency of primaryantenna 150.

FIG. 13 depicts an additional embodiment illustrating a self-resonanttransmitter circuit employing a modified class D amplifier for use withresonant frequency matching methods. Modified class D amplifier 1600 maybe used in place of, or in addition to, any or all of the elements ofexternal unit 120 depicted in FIG. 3. For example, modified class Damplifier 1600 may replace signal source 142 and amplifier 146. In thisembodiment, processor 144 may be configured to adjust the operation of aclass D amplifier to provide a frequency match between a generatedsignal and a resonant frequency of a primary antenna 150. Because theresonant frequency of primary antenna 150 may be adjusted to match thatof secondary antenna 152 during operation, it may be beneficial toadjust the frequency of the generated signal as well to improveefficiency within the self-resonant transmitter circuit of an externalunit 120. Modified class D amplifier 1600 may be used to provide such anadjustment as follows. Modified class D amplifier 1600 includes an Hbridge 1601 including switches (such as MOSFETs) 1620. Between theswitches is self-resonant transmitter circuit 1610. Power to themodified class amplifier is supplied by supply voltage 1650, which maybe supplied from a battery, for example. As shown in FIG. 13,self-resonant transmitter circuit 1610 may include multiple capacitances1640 and inductances 1660. Capacitances 1640 may include multiplecapacitors, combinations of which may be chosen from among trimcapacitors as described above, in order to selectively provide anappropriate value of capacitance 1640. The value of capacitance 1640 maybe selected for resonant frequency matching to secondary antenna 152.Inductances 1660 may be provided at least partially by primary antenna150. Processor 144 may also adjust a driving frequency of the H bridgeswitches 1620 in order to generate a signal of a frequency that matchesthe resonant frequency of self-resonant circuit 1610. By selectivelyopening and closing switches 1620 appropriately, the DC signal of supplyvoltage 1650 may be converted into a square wave of a selectedfrequency. This frequency may be selected to match the resonantfrequency of self-resonant circuit 1610 in order to increase theefficiency of the circuit.

FIG. 14 depicts an additional embodiment illustrating a pulsed modeself-resonant transmitter 1700 for use with resonant frequency matchingmethods. Pulsed mode self-resonant transmitter 1700 may be used in placeof, or in addition to, any or all of the elements of external unit 120depicted in FIG. 3. For example, pulsed mode self-resonant transmitter1700 may replace signal source 142 and amplifier 146. In thisembodiment, processor 144 may be configured to control the circuitthrough a power switching unit, depicted in the present embodiment asswitch 1730. A power switching unit may include a transistor, relay, orsimilar switching device. Pulsed mode self-resonant transmitter 1700 mayinclude a primary power source 1780, for example, a battery oralternative source of power. Transmitter 1700 may include a powerstorage unit, such as storage capacitor 1750. Other suitable powerstorage units may also be utilized, such as an inductor and/or battery,as well as combinations of these storage elements. Transmitter 1700 mayalso include a self-resonant transmitter circuit 1710, includingresonance capacitance 1720 and a resonance inductance 1760. Resonanceinductance 1760 may be provided at least partially by primary antenna150.

Transmitter 1700 may operate in the following manner, among others. Forexample, processor 144 may control the operation of switch 1730. Whenswitch 1730 is maintained in an open position, current from power source1780 may flow into storage capacitor 1750, which may thereby accumulatean electrical charge. When switch 1730 is closed, charged storagecapacitor 1750 may drive current into the self-resonant circuit 1710during a current loading period, where energy may be stored ininductance 1760. Due to the operation of diode 1770, current flow intocircuit 1710 may be cut off after a period of energy accumulation. Thecurrent transferred to circuit 1710 may then oscillate freely withincircuit 1710 at the resonant frequency of circuit 1710, and thusgenerate a signal for transmission to the implant through primaryantenna 150 (which is included in the circuit and creates at least aportion of inductance 1760). Because the signal is generated by the selfresonance of circuit 1710, it will match the resonant frequency ofcircuit 1710 and a more efficient transmission may be created.

Components of transmitter 1700 may be chosen such that the currentloading period may be approximately two microseconds and a period offree oscillation in circuit 1710 may be between 10 and 20 microseconds.Other components may be selected, however, to provide any desiredcurrent loading period or free oscillation period. As describedelsewhere in this disclosure, stimulation pulses of varying lengths maybe desired. Stimulation pulses of longer than a single period of freeoscillation may be constructed by multiple cycles of loading andreleasing energy from storage capacitor 1760 into circuit 1710. Storagecapacitor 1750 may itself be chosen to store enough charge to drive alarge number of oscillation cycles (e.g. between 10 and 100) in order toconstruct entire stimulation pulses without requiring recharging frompower source 1780.

Pulsed mode self-resonant transmitter 1700 may provide severaladvantages. As described above, because the transmission signal isgenerated by the self-resonance of circuit 1710, it likely will matchthe resonant frequency of circuit 1710, obviating a need to match thefrequency of the generated signal with the circuit resonance frequency.Further, because energy is stored in capacitor 1750 prior to dischargeinto circuit 1710, a greater flexibility in choice of power source 1780may be provided. Effective neural stimulation may depend on currentlevels that rise rapidly. To achieve this with a battery alone mayrequire a high-voltage and/or high-current battery. This need may beobviated by transmitter 1700, which permits the delivery of a very highpeak current through the use of a relatively low voltage/low currentbattery. Transmitter 1700 may use fewer switches (e.g. transistors) thandoes a conventional amplifying circuit. Each switch may be a source ofenergy loss, contributing to an overall less efficient circuit. Thepresence of a single switch 1730 in transmitter 1700 may increase theefficiency of the circuit as a whole.

The field inducing signal may be generated as a result of conditioningof the secondary signal by circuitry 180. As shown in FIG. 6, circuitry170 of external unit 120 may be configured to generate an AC primarysignal on primary antenna 150 that may cause an AC secondary signal onsecondary antenna 152. In certain embodiments, however, it may beadvantageous (e.g., in order to generate a unidirectional electric fieldfor modulation of a nerve) to provide a DC field inducing signal atimplant electrodes 158 a and 158 b. To convert the AC secondary signalon secondary antenna 152 to a DC field inducing signal, circuitry 180 inimplant unit 110 may include an AC-DC converter. The AC to DC convertermay include any suitable converter known to those skilled in the art.For example, in some embodiments the AC-DC converter may includerectification circuit components including, for example, diode 156 andappropriate capacitors and resistors. In alternative embodiments,implant unit 110 may include an AC-AC converter, or no converter, inorder to provide an AC field inducing signal at implant electrodes 158 aand 158 b.

As noted above, the field inducing signal may be configured to generatean electric field between implant electrodes 158 a and 158 b. In someinstances, the magnitude and/or duration of the generated electric fieldresulting from the field inducing signal may be sufficient to modulateone or more nerves in the vicinity of electrodes 158 a and 158 b. Insuch cases, the field inducing signal may be referred to as a modulationsignal. In other instances, the magnitude and/or duration of the fieldinducing signal may generate an electric field that does not result innerve modulation. in such cases, the field inducing signal may bereferred to as a sub-modulation signal.

Various types of field inducing signals may constitute modulationsignals. For example, in some embodiments, a modulation signal mayinclude a moderate amplitude and moderate duration, while in otherembodiments, a modulation signal may include a higher amplitude and ashorter duration. Various amplitudes and/or durations of field-inducingsignals across electrodes 158 a, 158 b may result in modulation signals,and whether a field-inducing signal rises to the level of a modulationsignal can depend on many factors (e.g., distance from a particularnerve to be stimulated; whether the nerve is branched; orientation ofthe induced electric field with respect to the nerve; type of tissuepresent between the electrodes and the nerve; etc.).

Whether a field inducing signal constitutes a modulation signal(resulting in an electric field that may cause nerve modulation) or asub-modulation signal (resulting in an electric field not intended tocause nerve modulation) may ultimately be controlled by processor 144 ofexternal unit 120. For example, in certain situations, processor 144 maydetermine that nerve modulation is appropriate. Under these conditions,processor 144 may cause signal source 144 and amplifier 146 to generatea modulation control signal on primary antenna 150 (i.e., a signalhaving a magnitude and/or duration selected such that a resultingsecondary signal on secondary antenna 152 will provide a modulationsignal at implant electrodes 158 a and 158 b).

Processor 144 may be configured to limit an amount of energy transferredfrom external unit 120 to implant unit 110. For example, in someembodiments, implant unit 110 may be associated with a threshold energylimit that may take into account multiple factors associated with thepatient and/or the implant. For example, in some cases, certain nervesof a patient should receive no more than a predetermined maximum amountof energy to minimize the risk of damaging the nerves and/or surroundingtissue. Additionally, circuitry 180 of implant unit 110 may includecomponents having a maximum operating voltage or power level that maycontribute to a practical threshold energy limit of implant unit 110.Processor 144 may be configured to account for such limitations whensetting the magnitude and/or duration of a primary signal to be appliedto primary antenna 150.

In addition to determining an upper limit of power that may be deliveredto implant unit 110, processor 144 may also determine a lower powerthreshold based, at least in part, on an efficacy of the deliveredpower. The lower power threshold may be computed based on a minimumamount of power that enables nerve modulation (e.g., signals havingpower levels above the lower power threshold may constitute modulationsignals while signals having power levels below the lower powerthreshold may constitute sub-modulation signals).

A lower power threshold may also be measured or provided in alternativeways. For example, appropriate circuitry or sensors in the implant unit110 may measure a lower power threshold. A lower power threshold may becomputed or sensed by an additional external device, and subsequentlyprogrammed into processor 144, or programmed Into implant unit 110.Alternatively, implant unit 110 may be constructed with circuitry 180specifically chosen to generate signals at the electrodes of at leastthe lower power threshold. In still another embodiment, an antenna ofexternal unit 120 may be adjusted to accommodate or produce a signalcorresponding to a specific lower power threshold. The lower powerthreshold may vary from patient to patient, and may take into accountmultiple factors, such as, for example, modulation characteristics of aparticular patient's nerve fibers, a distance between implant unit 110and external unit 120 after implantation, and the size and configurationof implant unit components (e.g., antenna and implant electrodes), etc.

Processor 144 may also be configured to cause application of submodulation control signals to primary antenna 150. Such sub-modulationcontrol signals may include an amplitude and/or duration that result ina sub-modulation signal at electrodes 158 a, 158 b. While suchsub-modulation control signals may not result in nerve modulation, suchsub-modulation control signals may enable feedback-based control of thenerve modulation system. That is, in some embodiments, processor 144 maybe configured to cause application of a sub-modulation control signal toprimary antenna 150. This signal may induce a secondary signal onsecondary antenna 152, which, in turn, may induce a primary coupledsignal component on primary antenna 150.

To analyze the primary coupled signal component induced on primaryantenna 150, external unit 120 may include feedback circuit 148 (e.g., asignal analyzer or detector, etc.), which may be placed in direct orindirect communication with primary antenna 150 and processor 144.Sub-modulation control signals may be applied to primary antenna 150 atany desired periodicity. In some embodiments, the sub-modulation controlsignals may be applied to primary antenna 150 at a rate of one everyfive seconds (or longer). In other embodiments, the sub-modulationcontrol signals may be applied more frequently (e.g., once every twoseconds, once per second, once per millisecond, once per nanosecond, ormultiple times per second). Further, it should be noted that feedbackmay also be received upon application of modulation control signals toprimary antenna 150 those that result in nerve modulation), as suchmodulation control signals may also result in generation of a primarycoupled signal component on primary antenna 150.

The primary coupled signal component may be fed to processor 144 byfeedback circuit 148 and may be used as a basis for determining a degreeof coupling between primary antenna 150 and secondary antenna 152. Thedegree of coupling may enable determination of the efficacy of theenergy transfer between two antennas. Processor 144 may also use thedetermined degree of coupling in regulating delivery of power to implantunit 110.

Processor 144 may be configured with any suitable logic for determininghow to regulate power transfer to implant unit 110 based on thedetermined degree of coupling. For example, where the primary coupledsignal component indicates that a degree of coupling has changed from abaseline coupling level, processor 144 may determine that secondaryantenna 152 has moved with respect to primary antenna 150 (either incoaxial offset, lateral offset, or angular offset, or any combination).Such movement, for example, may be associated with a movement of theimplant unit 110, and the tissue that it is associated with based on itsimplant location. Thus, in such situations, processor 144 may determinethat modulation of a nerve in the patients body is appropriate. Moreparticularly, in response to an indication of a change in coupling,processor 144, in some embodiments, may cause application of amodulation control signal to primary antenna 150 in order to generate amodulation signal at implant electrodes 158 a, 158 b, e.g., to causemodulation of a nerve of the patient.

In an embodiment for the treatment of OSA, movement of an implant unit110 may be associated with movement of the tongue, which may indicatethe onset of a sleep apnea event or a sleep apnea precursor. The onsetof a sleep apnea event or sleep apnea precursor may require thestimulation of the genioglossus muscle of the patient to relieve oravert the event. Such stimulation may result in contraction of themuscle and movement of the patient's tongue away from the patient'sairway.

In embodiments for the treatment of head pain, including migraines,processor 144 may be configured to generate a modulation control signalbased on a signal from a user, for example, or a detected level ofneural activity in a sensory neuron (e.g. the greater occipital nerve ortrigeminal nerve) associated with head pain. A modulation control signalgenerated by the processor and applied to the primary antenna 150 maygenerate a modulation signal at implant electrodes 158 a, 158 b, e.g.,to cause inhibition or blocking of a sensory nerve of the patient. Suchinhibition or blocking may decrease or eliminate the sensation of painfor the patient.

In embodiments for the treatment of hypertension, processor 144 may beconfigured to generate a modulation control signal based on, forexample, pre-programmed instructions and/or signals from an implantindicative of blood pressure. A modulation control signal generated bythe processor and applied to the primary antenna 150 may generate amodulation signal at implant electrodes 158 a, 158 b, e.g., to causeeither inhibition or stimulation of nerve of a patient, depending on therequirements. For example, a neuromodulator placed in a carotid arteryor jugular artery (i.e. in the vicinity of a carotid baroreceptor), mayreceive a modulation control signal tailored to induce a stimulationsignal at the electrodes, thereby causing the glossopharyngeal nerveassociated with the carotid baroreceptors to fire at an increased ratein order to signal the brain to lower blood pressure. Similar modulationof the glossopharyngeal nerve may be achieved with a neuromodulatorimplanted in a subcutaneous location in a patient's neck or behind apatient's ear. A neuromodulator place in a renal artery may receive amodulation control signal tailored to cause an inhibiting or blockingsignal at the electrodes, thereby inhibiting a signal to raise bloodpressure carried from the renal nerves to the kidneys.

Modulation control signals may include stimulation control signals, andsub-modulation control signals may include sub-stimulation controlsignals. Stimulation control signals may have any amplitude, pulseduration, or frequency combination that results in a stimulation signalat electrodes 158 a, 158 b. In some embodiments e.g., at a frequency ofbetween about 6.5-13.6 MHz), stimulation control signals may include apulse duration of greater than about 50 microseconds and/or an amplitudeof approximately 0.5 amps, or between 0.1 amps and 1 amp, or between0.05 amps and 3 amps. Sub-stimulation control signals may have a pulseduration less than about 500, or less than about 200 nanoseconds and/oran amplitude less than about 1 amp, 0.5 amps, 0.1 amps, 0.05 amps, or0.01 amps. Of course, these values are meant to provide a generalreference only, as various combinations of values higher than or lowerthan the exemplary guidelines provided may or may not result in nervestimulation.

In some embodiments, stimulation control signals may include a pulsetrain, wherein each pulse includes a plurality of sub-pulses. Analternating current signal (e.g., at a frequency of between about6.5-13.6 MHz) may be used to generate the pulse train, as follows. Asub-pulse may have a duration of between 50-250 microseconds, or aduration of between 1 microsecond and 2 milliseconds, during which analternating current signal is turned on. For example, a 200 microsecondsub-pulse of a 10 MHz alternating current signal will includeapproximately 2000 periods. Each pulse may, in turn, have a duration ofbetween 100 and 500 millisecond, during which sub pulses occur at afrequency of between 25 and 100 Hz. For example, a 200 millisecond pulseof 50 Hz sub-pulses will include approximately 10 sub-pulses. In in apulse train, each pulse may be separated from the next by a duration ofbetween 0.2 and 2 seconds. For example, in a pulse train of 200millisecond pulses, each separated by 1.3 seconds from the next, a newpulse will occur every 1.5 seconds. A pulse train of this embodiment maybe utilized, for example, to provide ongoing stimulation during atreatment session. In the context of OSA, a treatment session may be aperiod of time during which a subject is asleep and in need of treatmentto prevent OSA. Such a treatment session may last anywhere from aboutthree to ten hours, in the context of other conditions to which neuralmodulators of the present disclosure are applied, a treatment sessionmay be of varying length according to the duration of the treatedcondition.

Processor 144 may be configured to determine a degree of couplingbetween primary antenna 150 and secondary antenna 152 by monitoring oneor more aspects of the primary coupled signal component received throughfeedback circuit 148. In some embodiments, processor 144 may determine adegree of coupling between primary antenna 150 and secondary antenna 152by monitoring a voltage level associated with the primary coupled signalcomponent, a current level, or any other attribute that may depend onthe degree of coupling between primary antenna 150 and secondary antenna152. For example, in response to periodic sub modulation signals appliedto primary antenna 150, processor 144 may determine a baseline voltagelevel or current level associated with the primary coupled signalcomponent. This baseline voltage level, for example, may be associatedwith a range of movement of the patient's tongue when a sleep apneaevent or its precursor is not occurring, e.g. during normal breathing.As the patient's tongue moves toward a position associated with a sleepapnea event or its precursor, the coaxial, lateral, or angular offsetbetween primary antenna 150 and secondary antenna 152 may change. As aresult, the degree of coupling between primary antenna 150 and secondaryantenna 152 may change, and the voltage level or current level of theprimary coupled signal component on primary antenna 150 may also change.Processor 144 may be configured to recognize a sleep apnea event or itsprecursor when a voltage level, current level, or other electricalcharacteristic associated with the primary coupled signal componentchanges by a predetermined amount or reaches a predetermined absolutevalue.

FIG. 7 provides a graph that illustrates this principle in more detail.For a two-coil system where one col receives a radio frequency (RF)drive signal, graph 200 plots a rate of change in induced current in thereceiving coil as a function of coaxial distance between the coils. Forvarious coil diameters and initial displacements, graph 200 illustratesthe sensitivity of the induced current to further displacement betweenthe coils, moving them either closer together or further apart. It alsoindicates that, overall, the induced current in the secondary coil willdecrease as the secondary coil is moved away from the primary, drivecoil, i.e. the rate of change of induced current, in mA/mm, isconsistently negative. The sensitivity of the induced current to furtherdisplacement between the coils may vary with distance. For example, at aseparation distance of 10 mm, the rate of change in current as afunction of additional displacement in a 14 mm coil is approximately −6mA/mm. If the displacement of the coils is approximately 22 mm, the rateof change in the induced current in response to additional displacementis approximately −11 mA/mm, which corresponds to a local maximum in therate of change of the induced current. Increasing the separationdistance beyond 22 mm continues to result in a decline in the inducedcurrent in the secondary coil, but the rate of change decreases. Forexample, at a separation distance of about 30 mm, the 14 mm coilexperiences a rate of change in the induced current in response toadditional displacement of about −8 mA/mm. With this type ofinformation, processor 144 may be able to determine a particular degreeof coupling between primary antenna 150 and secondary antenna 152, atany given time, by observing the magnitude and/or rate of change in themagnitude of the current associated with the primary coupled signalcomponent on primary antenna 150.

Processor 144 may be configured to determine a degree of couplingbetween primary antenna 150 and secondary antenna 152 by monitoringother aspects of the primary coupled signal component. For example, insome embodiments, the non-linear behavior of circuitry 180 in implantunit 110 may be monitored to determine a degree of coupling. Forexample, the presence, absence, magnitude, reduction and/or onset ofharmonic components in the primary coupled signal component on primaryantenna 150 may reflect the behavior of circuitry 180 in response tovarious control signals (either sub-modulation or modulation controlsignals) and, therefore, may be used to determine a degree of couplingbetween primary antenna 150 and secondary antenna 152.

As shown in FIG. 6, circuitry 180 in implant unit 110 may constitute anon-linear circuit due, for example, to the presence of non-linearcircuit components, such as diode 156. Such non-linear circuitcomponents may induce non-linear voltage responses under certainoperation conditions. Non-linear operation conditions may be inducedwhen the voltage potential across diode 156 exceeds the activationthreshold for diode 156. Thus, when implant circuitry 180 is excited ata particular frequency, this circuit may oscillate at multiplefrequencies. Spectrum analysis of the secondary signal on secondaryantenna 152, therefore, may reveal one or more oscillations, calledharmonics, that appear at certain multiples of the excitation frequency.Through coupling of primary antenna 150 and secondary antenna 152, anyharmonics produced by implant circuitry 180 and appearing on secondaryantenna 152 may also appear in the primary coupled signal componentpresent on primary antenna 150.

In certain embodiments, circuitry 180 may include additional circuitcomponents that alter the characteristics of the harmonics generated incircuitry 180 above a certain transition point. Monitoring how thesenon-linear harmonics behave above and below the transition point mayenable a determination of a degree of coupling between primary antenna150 and secondary antenna 152. For example, as shown in FIG. 6,circuitry 180 may include a harmonics modifier circuit 164, which mayinclude any electrical components that non-linearly alter the harmonicsgenerated in circuitry 180. In some embodiments, harmonics modifiercircuit 154 may include a pair of Zener diodes. Below a certain voltagelaud, these Zener diodes remain forward biased such that no current willflow through either diode. Above the breakdown voltage of the Zenerdiodes, however, these devices become conductive in the reversed biaseddirection and will allow current to flow through harmonics modifiercircuit 154. Once the Zener diodes become conductive, they begin toaffect the oscillatory behavior of circuitry 180, and, as a result,certain harmonic oscillation frequencies may be affected (e.g., reducedin magnitude).

FIGS. 8 and 9 illustrate this effect. For example, FIG. 8 illustrates agraph 300 a that shows the oscillatory behavior of circuitry 180 atseveral amplitudes ranging from about 10 nanoamps to about 20 microamps.As shown, the primary excitation frequency occurs at about 87 MHz andharmonics appear both at even and odd multiples of the primaryexcitation frequency. For example, even multiples appear at twice theexcitation frequency (peak 302 a), four times the excitation frequency(peak 304 a) and six times the excitation frequency (peak 306 a). As theamplitude of the excitation signal rises between 10 nanoamps and 40microamps, the amplitude of peaks 302 a, 304 a, and 306 a all increase.

FIG. 9 illustrates the effect on the even harmonic response of circuitry180 caused by harmonics modifier circuit 154. FIG. 9 illustrates a graph300 b that shows the oscillatory behavior of circuitry 180 at severalamplitudes ranging from about 30 microamps to about 100 microamps. As inFIG. 8, FIG. 9 shows a primary excitation frequency at about 6.7 andsecond, fourth, and sixth order harmonics (peaks 302 b, 304 b, and 306b, respectively) appearing at even multiples of the excitationfrequency. As the amplitude of the excitation signal rises, however,between about 30 microamps to about 100 microamps, the amplitudes ofpeaks 302 b, 304 b, and 306 b do not continuously increase. Rather, theamplitude of the second order harmonics decreases rapidly above acertain transition level (e.g., about 80 microamps in FIG. 8). Thistransition level corresponds to the level at which the Zener diodesbecome conductive in the reverse biased direction and begin to affectthe oscillatory behavior of circuit 180.

Monitoring the level at which this transition occurs may enable adetermination of a degree of coupling between primary antenna 150 andsecondary antenna 152. For example, in some embodiments, a patient mayattach external unit 120 over an area of the skin under which implantunit 110 resides. Processor 144 can proceed to cause a series ofsub-modulation control signals to be applied to primary antenna 150,which in turn cause secondary signals on secondary antenna 152. Thesesub-modulation control signals may progress over a sweep or scan ofvarious signal amplitude levels. By monitoring the resulting primarycoupled signal component on primary antenna 150 (generated throughcoupling with the secondary signal on secondary antenna 152), processor144 can determine the amplitude of primary signal (whether asub-modulation control signal or other signal) that results in asecondary signal of sufficient magnitude to activate harmonics modifiercircuit 154. That is, processor 144 can monitor the amplitude of thesecond, fourth, or sixth order harmonics and determine the amplitude ofthe primary signal at which the amplitude of any of the even harmonicsdrops. FIGS. 8 and 9 illustrate the principles of detecting couplingthrough the measurement of non-linear harmonics. These Figuresillustrate data based around a 6.7 MHz excitation frequency. Theseprinciples, however, are not limited to the 6.7 MHz excitation frequencyillustrated, and may be used with a primary signal of any suitablefrequency.

In some embodiments, the determined amplitude of the primary signalcorresponding to the transition level of the Zener diodes (which may bereferred to as a primary signal transition amplitude) may establish abaseline range when the patient attaches external unit 120 to the skin.Presumably, while the patient is awake, the tongue is not blocking thepatient's airway and moves with the patients breathing in a naturalrange, where coupling between primary antenna 150 and secondary antenna152 may be within a baseline range. A baseline coupling range mayencompass a maximum coupling between primary antenna 150 and secondaryantenna 152. A baseline coupling range may also encompass a range thatdoes not include a maximum coupling level between primary antenna 150and secondary antenna 152. Thus, the initially determined primary signaltransition amplitude may be fairly representative of a non-sleep apneacondition and may be used by processor 144 as a baseline in determininga degree of coupling between primary antenna 150 and secondary antenna152. Optionally, processor 144 may also be configured to monitor theprimary signal transition amplitude over a series of scans and selectthe minimum value as a baseline, as the minimum value may correspond toa condition of maximum coupling between primary antenna 150 andsecondary antenna 152 during normal breathing conditions.

As the patient wears external unit 120, processor 144 may periodicallyscan over a range of primary signal amplitudes to determine a currentvalue of the primary signal transition amplitude. In some embodiments,the range of amplitudes that processor 144 selects for the scan may bebased on (e.g., near) the level of the baseline primary signaltransition amplitude, if a periodic scan results in determination of aprimary signal transition amplitude different from the baseline primarysignal transition amplitude, processor 144 may determine that there hasbeen a change from the baseline initial conditions. For example, in someembodiments, an increase in the primary signal transition amplitude overthe baseline value may indicate that there has been a reduction in thedegree of coupling between primary antenna 150 and secondary antenna 152(e.g., because the implant has moved or an internal state of the implanthas changed).

In addition to determining whether a change in the degree of couplinghas occurred, processor 144 may also be configured to determine aspecific degree of coupling based on an observed primary signaltransition amplitude. For example, in some embodiments, processor 144may have access to a lookup table or a memory storing data thatcorrelates various primary signal transition amplitudes with distances(or any other quantity indicative of a degree of coupling) betweenprimary antenna 150 and secondary antenna 152. In other embodiments,processor 144 may be configured to calculate a degree of coupling basedon performance characteristics of known circuit components.

By periodically determining a degree of coupling value, processor 144may be configured to determine, in situ, appropriate parameter valuesfor the modulation control signal that will ultimately result in nervemodulation. For example, by determining the degree of coupling betweenprimary antenna 150 and secondary antenna 152, processor 144 may beconfigured to select characteristics of the modulation control signal(e.g., amplitude, pulse duration, frequency, etc.) that may provide amodulation signal at electrodes 158 a, 158 b in proportion to orotherwise related to the determined degree of coupling. In someembodiments, processor 144 may access a lookup table or other datastored in a memory correlating modulation control signal parametervalues with degree of coupling. In this way, processor 144 may adjustthe applied r modulation control signal in response to an observeddegree of coupling.

Additionally or alternatively, processor 144 may be configured todetermine the degree of coupling between primary antenna 150 andsecondary antenna 152 during modulation. The tongue, or other structureon or near which the implant is located, and thus implant unit 110, maymove as a result of modulation. Thus, the degree of coupling may changeduring modulation. Processor 144 may be configured to determine thedegree of coupling as it changes during modulation, in order todynamically adjust characteristics of the modulation control signalaccording to the changing degree of coupling. This adjustment may permitprocessor 144 to cause implant unit 110 to provide an appropriatemodulation signal at electrodes 158 a, 158 b throughout a modulationevent. For example, processor 144 may alter the primary signal inaccordance with the changing degree of coupling in order to maintain aconstant modulation signal, or to cause the modulation signal to bereduced in a controlled manner according to patient needs.

More particularly, the response of processor 144 may be correlated tothe determined degree of coupling. In situations where processor 144determines that the degree of coupling between primary antenna 150 andsecondary antenna has fain only slightly below a predetermined couplingthreshold (e.g., during snoring or during a small vibration of thetongue or other sleep apnea event precursor), processor 144 maydetermine that only a small response is necessary. Thus, processor 144may select modulation control signal parameters that will result in arelatively small response (e.g., a short stimulation of a nerve, smallmuscle contraction, etc. Where, however, processor 144 determines thatthe degree of coupling has fallen substantially below the predeterminedcoupling threshold (e.g., where the tongue has moved enough to cause asleep apnea event), processor 144 may determine that a larger responseis required. As a result, processor 144 may select modulation controlsignal parameters that will result in a larger response. In someembodiments, only enough power may be transmitted to implant unit 110 tocause the desired level of response. In other words, processor 144 maybe configured to cause a metered response based on the determined degreeof coupling between primary antenna 150 and secondary antenna 152. Asthe determined degree of coupling decreases, processor 144 may causetransfer of power in increasing amounts. Such an approach may preservebattery life in the external unit 120, may protect circuitry 170 andcircuitry 180, may increase effectiveness in addressing the type ofdetected condition (e.g., sleep apnea, snoring, tongue movement, etc.),and may be more comfortable for the patient.

In some embodiments, processor 144 may employ an iterative process inorder to select modulation control signal parameters that result in adesired response level. For example, upon determining that a modulationcontrol signal should be generated, processor 144 may cause generationof an initial modulation control signal based on a set of predeterminedparameter values. If feedback from feedback circuit 148 indicates that anerve has been modulated (e.g, if an increase in a degree of coupling isobserved), then processor 144 may return to a monitoring mode by issuingsub-modulation control signals. If, on the other hand, the feedbacksuggests that the intended nerve modulation did not occur as a result ofthe intended modulation control signal or that modulation of the nerveoccurred but only partially provided the desired result (e.g, movementof the tongue only partially away from the airway), processor 144 maychange one or more parameter values associated with the modulationcontrol signal (e.g., the amplitude, pulse duration, etc.).

Where no nerve modulation occurred, processor 144 may increase one ormore parameters of the modulation control signal periodically until thefeedback indicates that nerve modulation has occurred. Where nervemodulation occurred, but did not produce the desired result, processor144 may re-evaluate the degree of coupling between primary antenna 150and secondary antenna 152 and select new parameters for the modulationcontrol signal targeted toward achieving a desired result. For example,where stimulation of a nerve causes the tongue to move only partiallyaway from the patient's airway, additional stimulation may be desired.Because the tongue has moved away from the airway, however, implant unit110 may be closer to external unit 120 and, therefore, the degree ofcoupling may have increased. As a result, to move the tongue a remainingdistance to a desired location may require transfer to implant unit 110of a smaller amount of power than what was supplied prior to the laststimulation-induced movement of the tongue. Thus, based on a newlydetermined degree of coupling, processor 144 can select new parametersfor the stimulation control signal aimed at moving the tongue theremaining distance to the desired location.

In one mode of operation, processor 144 may be configured to sweep overa range of parameter values until nerve modulation is achieved. Forexample, in circumstances where an applied sub-modulation control signalresults in feedback indicating that nerve modulation is appropriate,processor 144 may use the last applied sub-modulation control signal asa starting point for generation of the modulation control signal. Theamplitude and/or pulse duration (or other parameters) associated withthe signal applied to primary antenna 150 may be iteratively increasedby predetermined amounts and at a predetermined rate until the feedbackindicates that nerve modulation has occurred.

Processor 144 may be configured to determine or derive variousphysiologic data based on the determined degree of coupling betweenprimary antenna 150 and secondary antenna 152. For example, in someembodiments the degree of coupling may indicate a distance betweenexternal unit 120 and implant unit 110, which processor 144 may use todetermine a position of external unit 120 or a relative position of apatient's tongue. Monitoring the degree of coupling can also providesuch physiologic data as whether a patient's tongue is moving orvibrating (e.g. whether the patient is snoring), by how much the tongueis moving or vibrating, the direction of motion of the tongue, the rateof motion of the tongue, etc.

In response to any of these determined physiologic data, processor 144may regulate delivery of power to implant unit 110 based on thedetermined physiologic data. For example, processor 144 may selectparameters for a particular modulation control signal or series ofmodulation control signals for addressing a specific condition relatingto the determined physiologic data. If the physiologic data indicatesthat the tongue is vibrating, for example, processor 144 may determinethat a sleep apnea event is likely to occur and may issue a response bydelivering power to implant unit 110 in an amount selected to addressthe particular situation, if the tongue is in a position blocking thepatient's airway (or partially; blocking a patient's airway), but thephysiologic data indicates that the tongue is moving away from theairway, processor 144 may opt to not deliver power and wait to determineif the tongue clears on its own. Alternatively, processor 144 maydeliver a small amount of power to implant unit 110 (e.g., especiallywhere a determined rate of movement indicates that the tongue is movingslowly away from the patient's airway) to encourage the tongue tocontinue moving away from the patient's airway or to speed itsprogression away from the airway. The scenarios described are exemplaryonly. Processor 144 may be configured with software and/or logicenabling it to address a variety of different physiologic scenarios withparticularity. In each case, processor 144 may be configured to use thephysiologic data to determine an amount of power to be delivered toimplant unit 110 in order to modulate nerves associated with the tonguewith the appropriate amount of energy.

The disclosed embodiments may be used in conjunction with a method forregulating delivery of power to an implant unit. The method may includedetermining a degree of coupling between primary antenna 150 associatedwith external unit 120 and secondary antenna 152 associated with implantunit 110, implanted in the body of a patient. Determining the degree ofcoupling may be accomplished by processor 144 located external toimplant unit 110 and that may be associated with external unit 120.Processor 144 may be configured to regulate delivery of power from theexternal unit 120 to the implant unit 110 based on the determined degreeof coupling.

As previously discussed, the degree of coupling determination may enablethe processor to further determine a location of the implant unit. Themotion of the implant unit may correspond to motion of the body partwhere the implant unit may be attached. This may be consideredphysiologic data received by the processor. The processor may,accordingly, be configured to regulate delivery of power from the powersource to the implant unit based on the physiologic data. In alternativeembodiments, the degree of coupling determination may enable theprocessor to determine information pertaining to a condition of theimplant unit. Such a condition may include location as well asinformation pertaining to an internal state of the Implant unit. Theprocessor may, according to the condition of the implant unit, beconfigured to regulate delivery of power from the power source to theimplant unit based on the condition data.

In some embodiments, implant unit 110 may include a processor located onthe implant. A processor located on implant unit 110 may perform all orsome of the processes described with respect to the at least oneprocessor associated with an external unit. For example, a processorassociated with implant unit 110 may be configured to receive a controlsignal prompting the implant controller to turn on and cause amodulation signal to be applied to the implant electrodes for modulatinga nerve. Such a processor may also be configured to monitor varioussensors associated with the implant unit and to transmit thisinformation back to external unit 120. Power for the processor unit maybe supplied by an onboard power source or received via transmissionsfrom an external unit.

In other embodiments, implant unit 110 may be self-sufficient, includingits own power source and a processor configured to operate the implantunit 110 with no external interaction. For example, with a suitablepower source, the processor of implant unit 110 may be configured tomonitor conditions in the body of a subject (via one or more sensors orother means), determining when those conditions warrant modulation of anerve, and generate a signal to the electrodes to modulate a nerve. Thepower source co yid be regenerative based on movement or biologicalfunction; or the power sources could be periodically rechargeable froman external location, such as, for example, through induction.

Other embodiments of the present disclosure will be apparent to thosespilled in the art from consideration of the specification and practiceof the present disclosure.

Additional aspects of the invention are described in the followingnumbered paragraphs, which are part of the description of exemplaryembodiments of the invention. Each numbered paragraph stands on its ownas a separate embodiment of the invention.

The invention claimed is:
 1. A device for treating sleep apnea byconveying power from a location external to a subject to a locationwithin the subject, the device comprising: a flexible carrier; anadhesive on a first side of the flexible carrier; a coil of electricallyconductive material associated with the flexible carrier, the coilconfigured to facilitate power transfer to an implant proximate agenioglossus muscle of a subject; a mechanical connector associated withthe carrier opposite the adhesive, wherein the mechanical connector isconfigured to retain a housing including a power source including apower source and permit the housing to rotate relative to the flexiblecarrier; and at least one electrical portion associated with theflexible carrier in a manner permitting electrical connection to bemaintained between the flexible carrier and the power source as thehousing is rotated, to enable powering of the implant.
 2. The device ofclaim 1, wherein the mechanical connector is configured to permit morethan about 360-degree rotation of the housing relative to the flexiblecarrier.
 3. The device of claim 1, wherein the mechanical connector isconfigured to permit rotation of less than about 360-degree rotation ofthe housing relative to the flexible carrier.
 4. The device of claim 1,wherein the at least one electrical portion includes conductive materialarranged in concentric rings.
 5. The device of claim 1, wherein the atleast one electrical portion includes a pattern of discontinuousconductive material arranged on the flexible carrier.
 6. The device ofclaim 1, wherein the at least one electrical portion includes conductivematerial arranged in a plurality of arcs.